Kumanaku is a troop member of the 1st Division of Shinsengumi, led by Captain Okita Sougo.
Already well known among the ranks as a cleanliness freak, he observed that the toilets in the headquarters are really filthy and that it was a result of ill-discipline among troop members. He made a fervent plea for a complete overhaul of mindset, even going up to Hijikata Toushirou with his proposal for a Toilet Revolution. Hijikata was bought over by his plan and the 3 of them, Hijikata, Okita and Kumanaku tried various plans to get troop members to adopt more hygienic toilet habits. Thereafter the scheme merged with Hijikata's dream, which was a parody of Miyazaki Hayao's animated film, Nausicaa.
He has mole on his forehead, until Okita scrubbed it off with a toilet brush. His mole was subsequently used by Okita as a target point on the urinal to get troops members to aim their pee more accurately.
He has just been transferred to the 1st division under Okita during his first appearance. During the Toilet Revolution, his mole is being removed by Okita. He is nowhere to be seen afterwards until the end of Farewell, Shinsengumi arc. He is among the survivors of the battle and heads towards the universe with his colleagues.