Seki is playing a lucky laugher game, in which someone is blindfolded and they have to put a face together and people laugh the funny face that is made. This game is traditionally played at New Years in Japan, but Seki is not one for adhering to traditions. While Seki initially gets the face wrong, he quickly gets it right, although for Rumi it isn’t as the face has a pompadour hairstyle - a stereotypical do for a young street punk. However, this street punk has gotten married and has had a baby, as a baby face and and a lady face have been created, so street punk reforms and gets a more respectable hairstyle. The baby continues to grow and grow, eventually standing up and celebrating the 7-5-3 festival, which is a Japanese rite of passage celebrated by children in November who are 7, 5, and 3. The child begins attending school, but Rumi notices that the parents are drifting further and further away, so attempts to blow them back together, but Seki’s hand gets in the way and the sudden rush of air, spooks him.

There aren’t enough printouts for everyone in the class, so those in the back of the classroom (such as Rumi and Seki) have to share, which is a bother for Seki as he can’t reach his bag (of tricks) as Rumi's desk is in the way. However, he can still play around as he has a deck of cards in his pencil case. He tries to impress Rumi with his card tricks, but she is having none of it and even crumples a card he placed under the first sheet of the printout, which he had just shown her. That same card appears on Maeda's (a classmate of theirs) butt, so when Rumi checks the crumpled card it is now a different card and when she respectfully looks back at Maeda's butt, that card has disappeared and is now appearing out of Seki’s mouth. Class is now over.

It is lunchtime and Seki has made octopus hot dogs (mini hot dog sausages cut in half and had the flat end cut up so it looks like tentacles) and is eating them with malice. The octopus hot dogs try to 'defend' themselves by linking 'tentacles' but it is pointless as they are still devoured. One octopus hot dog, clad in tempura-batter armour and armed with an asparagus spear, attempts to fend off Seki, but is eaten pretty swiftly although he does cause Seki to choke, giving Rumi much Schadenfreude. Seki has had enough octopus hot dogs, so leaves them for his friends to have. He then gets some apple bunny slices (apple slices that have half the skin removed and ‘V’ cut into the skin that's left to make distinct ears) for inevitably the same to occur.

Seki is playing with Shogi pieces and it sees an entire 'army' against a pawn and a 'new' piece - princess. The pawn and the princess are in love, but the King forbids their relationship and has the army attack the pawn. After the attack, the pawn and the princess get married and the power of love grants the pawn he strength to fight back, but the princess is captured. The pawn is then also captured and then tortured. Rumi finds a Gold General piece on the floor that was knocked off in the pawn's attack, which is actually a 'father' piece - the father of the pawn. Rumi attempts to save the pawn with the father piece, but Seki blocks the way with his textbook. However, Seki has been called to read from his textbook so has to lift the barricade, although the other pieces have made a wall of their own. However, this is not enough to stop the father from freeing his son.

Maeda, the student who sits in front of Seki, is absent so Seki is in full view of the teacher and can't mess around today. However, that won't stop him as he plays darts with his feet and throws a dart that lands on a ring labelled Ikebana (flower arranging) and he attempts to do that using his feet. This is too difficult and he steps on the flower arranger. Rumi hands him a plaster and he tries to use his feet but, assumedly, uses his hands to put it on. Seki eventually arranges a small bouquet with his feet and throws another dart and selects heavy lifting, but the weight rolls away so he can't reach it with his feet.

Rumi and Seki's class are at a forest school for the day, which Seki visited when he was younger and is recognised by the staff as the "Devil" (self-titled). The main activity today is a hike in small groups to an observation deck and on the way, they find a carved wooden sign pointing to the Devil’s Castle. Seki is embarrassed by it and when no one is looking, takes the sign and stashes in his bag. Later on, their group stumbles on a lake which the "Devil" calls "Boiling Pond" (touching the water will burn you up and kill you) and everyone is laughing at the sign, except for Seki and Rumi, as the former is writhing in embarrassment and the latter feels bad for laughing at something a child made. They stumble on a grave of a dragon that will resurrect if you don't respect nature and buried is a 'sword' (a ruler with some twigs tied around it as a hilt) known as "Dragon Killer". Everyone else continues to laugh and this includes Rumi, but only because she suspects that Seki might have worked out that she knows that he was the ‘Devil’ and she needs to throw him off the scent. They arrive at the 'Devil's Castle', which is painted on a board and is in a tree and secured by some rope. Uzawa unties this rope, causing the castle to fall and along with a framed drawing of a 5 year old Seki as a knight, signed by a 5 year old Seki. Only Rumi finds this drawing and immediately takes possession of it to dispose of it later. They arrive at the observation deck and Rumi disposes of the drawing by throwing it into a nearby creek, but it floats into "Boiling Pond" and Rumi spots on the way back and quickly picks it up with her excuse being near the water's edge is that she was rinsing off her hands. However, the boys (including Seki) of her group begin laughing at her for risking burning herself up, so Seki's drawing is heading to Rumi’s room for safekeeping as blackmail material.

This chapter we have a 2nd narrator in the form of Goto, a classmate of Rumi and Seki, who wishes to be the friend of the former but the closest she gets to her is in art class. In an art lesson, Seki is playing table-top golf, with the dents in the table's surface serving as golf holes. Rumi assumes that Seki will be no good, owing to the uneven surface of the tables, but Seki manages to get his first shot in. After carefully looking at the terrain, he gets another hole-in-one, impressing Rumi, but Goto interprets this as a sign that Rumi is in love with Seki, as after all she is rumoured to have put a love letter in Seki's shoe locker. Seki is aiming for another hole (par of 2), which is next to Rumi and him gazing at the hole and Rumi looking back in anticipation of him making the shot is evidence for Goto to believe that they are secretly in a loving relationship. Goto sees this as an opportunity as a way to get closer to Rumi, while Rumi receives a set of printouts to pass on to those behind her and as she does this, she hits Seki's golf ball, knocking it off the table. Seki is now in a foul mood and Rumi apologises to him silently and this wordless conversation causes Goto to believe that the 2 live together and possibly make love together, although she believes that Rumi wouldn't want to as they are still too young. Seki, meanwhile, puts out a flag for Rumi to hold to indicate where the hole is on the table and after initially hesitating, she picks it up (this further secretive communication between the couple for Goto). Seki can't find his golf ball and he doesn't have any spares, so he and Rumi go under the table to look for it and Goto assumes it is for some quality time with one's lover.
During a break from lessons, Goto confronts Rumi about her 'playtime' with Seki and Rumi explains that Seki is always like this and she should probably get him to stop, but she gets sucked up into it. She is also glad to found someone who sees what she sees with regards to Seki, although Goto has got completely wrong idea as her idea of playtime is more sexual, but promises to support Rumi and this gets her to be Rumi's friend (mission accomplished?).

Seki is playing with Othello pieces and is drawing faces on both sides with the white sides having smiling faces as they are humans and the black sides having more evil expressions as they are zombies. He then begins to play othello properly (as much as one can alone) so when a white piece is captured, it instead infected and turned into a zombie. Soon there is only one human left but luckily it is out in the sun, where the zombie can't go, so Seki creates a shadow with his hand, putting the lone human in danger. Rumi comes to the human's rescue by reflecting light onto the human using a pocket mirror, so Seki tries to block the light using his text books, so Rumi uses her polished pencil board from 3rd Period (the chapter, not the lesson that day) only for Seki to stop playing and begin studying. Rumi is overjoyed at her apparent victory over Seki, but is short-lived as the teacher appears from behind her and scolds her for disrupting another student's study.

Rumi complains to Goto that Seki's antics are wearing her out and Goto believes that this is because Rumi spoiling him. Rumi publicly denies this, but privately she agrees with Goto and decides to not allow Seki to slack off so easily during the next lesson. In the next lesson, Seki is playing with Jenga and scared as Rumi nearly calls him out for playing around, but is saved by her pivoting to mistake on the board although he now has to hold a Jenga tower in his hand and can't it back the table for he will be immediately rumbled. He begins to build his Jenga tower on his hand with increasing speed, although high winds start to blow through as Rumi fans herself with a board and the tower begins the topple. Seki catches it with foot, so the tower now lays horizontal wedged between his hand and his foot, so continues to rearrange the tower while Rumi decides to flick a rubber at the tower, but pulls out at the last second as Seki has built a replica of the Tokyo Bay Rainbow Bridge using Jenga blocks and she can't wilfully destroy a thing of beauty. She is ok with letting him play this time as he knows he can no longer be so brazen with it, although from Goto's vantage point in the classroom, Rumi is still head over heels in love with Seki.

Seki has brought a conversation cube to class and is playing with despite we never hear him talk throughout the entire series. He rolls the cube and it lands on "embarrassing stories" and Rumi, who is trying to ignore him, remembers an embarrassing story. She was out shopping with her friends and they started talking about new shops, trends, and designers and she was at a loss because she doesn't keep up with such things. Meanwhile, Seki is majorly cringing at his own embarrassing story that he has remembered but he recovers to throw the dice again and lands on "sad stories". Rumi's mind drifts back to a time where she went to her brother's room to return a comic she borrowed only to be hit with a 50 yen (24p) borrowing fee that come into existence since she first borrowed the comic. She paid the fee without any complaints despite being disappointed in herself and her brother. Meanwhile, Seki is absolutely distraught but pulls through to throw the dice again and it lands o the same square again - "sad stories". Seki reaches for his thermos of tea anf begins to chug it down like a depressed alcoholic and in doing so knocks the dice off the table. Rumi notices the sad mood he is in and looks at the dice on the floor and ses that has changed to "funny stories" and points this out to Seki, who begins to silently laugh, just as the lesson ends.

Rumi and Seki's class are at the pool practising CPR and Seki has brought the robot family along who also are practising CPR. Everyone learns how to do CPR really quickly so the teacher allows them to play in the pool for the rest of the lesson. Seki abandons the family, so Rumi takes it upon herself to put the family in a safe space and arranges them on some conveniently nearby miniature deckchairs and pool. She heads back to the pool, only for the family to be discovered by chaos incarnate himself, Uzawa, who throws Kid-bot into the pool. Rumi goes in to try and retrieve it, only to lose sight of it after Maeda surges pass doing the butterfly stroke although spots it again tangled up in Goto's hair. Seki has also spotted it as well and by the time Rumi reaches Goto, Kid-bot is safe and sound with parents, splitting watermelons. The lesson comes to a close and Rumi has still not found Kid-bot.

Whilst cleaning the school corridor, Rumi spots Seki raking leaves earnestly outside, only for him suddenly disappear. She eventually spots him again, but only sort of while she doesn't see him, she does see a pile of leaves that moves. Seki sneaks up on another pile of leaves and takes them and takes them to a more secluded location where he arranges them like a bed and attempts sleep on by diving onto them. The leaves do not cushion the fall, so Seki starts to pile them up again, but retreats into the pile as soon as he hears someone approaching. The someone is a teacher who spots Seki's pile and dumps his supply of leaves before attempting to set on fire without realising that there might be a human-sized hedgehog hibernating inside. Seki life is spared when a mysterious voice (Rumi) calls out telling the teacher that the gym store room is on fire, triggering fire safety protocols. The 'fire' produces no direct casualties, but a girl comes down with a fever from guilt that night.

The stuff that lesson is focussing on is stuff that Rumi already dealt with at cram school, so she chooses not pay proper attention and instead focus of Seki's antics (Goto is right, you do spoil him too much). Today a mini teddy bear has gone camping and is looking through some binoculars at his fellow teddy bear who is scaling Mount Maeda thanks to some string tied around it and looped through a crocodile clip which is attached to the collar of Maeda' shirt. The climb is no easy feat as Mount Maeda shakes violently when he needs to rub something out, but the climber reaches the summit and pulls out a flag from their rucksack as celebration. However, there is nowhere safe on Mount Maeda, as when Maeda rolls his head back, he knocks climber-teddy off and through an open window, but Seki manages haul the teddy back up. After nearly being rumbled, losing a teddy bear, and being dissuaded by Rumi: Seki goes for another attempt, only forMaeda to turn around forcing him to cower behind a textbook who then switches his gaze on Rumi, who does the same as well despite not being an active participant in the fun.
The first set of bonus comics focus on our main characters on classroom duty during a lesson break. The 1st sees Seki cleans the chalkboard, while Rumi updates the class journal which surprises Goto who assumed that the pair would work together. The 2nd begins after school, with one of Rumi's friends looking for her to give her english notes as she couldn't study in that class (because she was too distracted by Seki). One of them decides to write a few words of encouragement for Rumi, which triggers a chain reaction that sees pretty much the entire class get involved. They all receive a thank you note the next day from Rumi.
The 2nd set of bonus comics stars Takuma Morishige and his quest to find a suitable barber as he doesn't want one too talkative nor that makes him look like Coach from Miracle (if you know, you knw because I sure don't).