Box of Happiness (
Summary[]
Kaigaku recalls his encounter with Kokushibo.
Kaigaku remembers his unfortunate encounter with Upper Rank One, remarking that it was not shameful to kneel before an overwhelmingly strong opponent. He believes that as long as he remains alive, it would all work out in the end. It does not matter if dirt is rubbed in his face, he is forced to drink dirty water, or people curse him for stealing money; what mattered was that he was alive and that someday, he would succeed. Kokushibo then asks if Kaigaku wants to become a demon and get stronger, drawing blood from his hand to drink. If Muzan recognizes him, he will transform into a demon.
He explains that to become one takes time, a process that is longer the stronger a person is; Kokushibo himself took three days to transform. Additionally, to counteract the effects of Total Concentration, much blood must be drunk, and rarely does a person's body not allow them to become a demon. Kokushibo tells the Demon Slayer to be grateful for the blood he received, threatening to behead him should he spill a drop. He reminisces on the intense fear he felt as he put the blood into his mouth, as if his cells were screaming and crying.
Compared to facing Zenitsu now, the Upper Rank is not worried. Despite gaining some strength, he believes Zenitsu remains a worthless coward, crying without dignity or perseverance. He recalls when Jigoro had offered to make them both his successors and curses his former trainer for comparing him to his junior. As he angrily declares that they both deserved to die, Kaigaku uses Thunder Breathing, Second Form: Rice Spirit, attacking Zenitsu with five consecutive slashes and injuring his face. Zenitsu remarks that with the consecutive attacks, Kaigaku has already eaten much victims, believing he can't tell good from evil anymore.
Kaigaku wounds Zenitsu with Sixth Form: Rumble and Flash.
Kaigaku responds he does know, using Third Form: Thunder Swarm to envelope Zenitsu in black lightning, burning him. The demon tells him the true difference is that those who know his worth are good and those who don't are evil. Using Fifth Form: Heat Lightning, Kaigaku slashes and burns Zenitsu simultaneously, asking if he enjoys his blade infused with his Blood Demon Art, before attacking him again with Sixth Form: Rumble and Flash, wounding Zenitsu all throughout his body; Kaigaku gloats that with his immense power both burning and slashing him, he has become a demon to surpass Thunder Breathing.
As Zenitsu falls, with the demon remarking he is truly different to him, he recalls Jigoro's lesson to use Kaigaku as an example; Thunder Breathing as a style revolves around using the first form as a foundation; as such, it didn't matter if someone could use the other forms when they could do the first. Knowing this, he recalls that even when Kaigaku was a lesser user of the style, he retained an arrogant personality, dismissing anyone who he perceived to be beneath him, despite himself knowing that Kaigaku could never be a Hashira as a result.
He understands why Kaigaku hates him, but despite also returning the sentiment, he still respected Kaigaku for his hard work. To him and Jigoro, Kaigaku was a special person, yet none of it satisfied him. He compares Kaigaku's heart to a box with a hole that held his happiness; despite whatever went in, it could never fill up.
Zenitsu beheads Kaigaku with Seventh Form: Honoikazuchi no Kami.
Apologizing to Jigoro for the two of them taking different paths, he uprights his body and plants his feet along the wall to stop his descent. As Kaigaku watches with surprise, Zenitsu apologizes to him and attacks with Thunder Breathing, Seventh Form: Honoikazuchi no Kami, instantly decapitating Upper Rank Six. As he plummets, Kaigaku tries to comprehend what had just happened, unable to see the rapid attack. He curses Jigoro for favoring Zenitsu by teaching him an exclusive form, but Zenitsu denies their trainer was such a person. This form is of his creation, one he had hoped to use to fight with him.
Characters in Order of Appearance[]
- Kokushibo (Flashback)
- Kaigaku
- Zenitsu Agatsuma
- Jigoro Kuwajima (Flashback)
Events[]
- Zenitsu Agatsuma vs Kaigaku.
- Kaigaku is revealed to have encountered Kokushibo, transforming into a demon to save himself.
- Kaigaku severely injures Zenitsu through multiple attacks.
- Zenitsu beheads Kaigaku with a self-taught seventh form of Thunder Breathing.