The protagonist of Spiral. Ayumu is very intelligent, but is very introverted and has a lot of self-doubt. He fears that he cannot surpass his own perfect older brother and doubts himself to the point where he no longer believes he can do anything anymore without acting like his brother. He is a talented pianist like Kiyotaka, an excellent cook, and cares a lot for his sister-in-law Madoka. Ayumu is also the supposed only hope for the Blade Children and their survival.

Spoiler

In the manga, it is later revealed he is the clone of Kiyotaka- and thus has a shorter lifespan. In the epilogue、it is shown that he is hospitalized due to complications and cannot use his left arm anymore and is visited by "Hiyono".