i think steampianist's thing really suits kabukimono. the speaker in the song struggles to convey emotions properly and wishes to have certain traits ("hair like yours," "hands like yours," "eyes to stare and to cry with," "fingers that curl in the cold"), which can be read as fervently coveting to look and feel "normal." or, in kabukimono's case, to look and feel human.

like the speaker in the song, kabukimono cannot understand or show certain emotions, and so he learns from those around him (like a sponge absorbing new information) about human life. he hides his true nature as a puppet and learns how to live as a human, but as human as he may act he can never truly be human if the parameters set for what it means to be human are that (1) you must have a heart and (2) your lifespan must be finite (which are parameters kabukimono thinks equals humanity). he has neither of these, which is why he never truly views himself as a human even though you could argue that being "human" simply means you are a complex individual who can feel, think, speak, and articulate (all things kabukimono is capable of).

as the song nears its conclusion, it's implied that the speaker hurt or killed their friends in some way, and you learn that all along this "thing" has wanted companionship and to feel and display emotions properly. but something goes wrong and the result is this eerie line: "struggling only makes the hugs much tighter." both kabukimono and the speaker in the song are driven by their obsessions, and both have bloodied their hands as the result of their circumstances (kabukimono's motivation for murder being revenge and the speaker's most likely being the threat of their friends leaving, so they become determined to make them stay even if it ends in death).

and by the end, the speaker still continues to wish for the traits mentioned above. likewise, kabukimono continues in his travels after sating his hunger for revenge and with "human" traits he has learned and experienced throughout his journey, only to soon step onto the path that leads him to becoming a harbinger once he comes to believe that his "humanity" is a sign of weakness. and so he does away with the things that made him human and starts a new era of his existence (albeit a more violent, cruel one), much like how the speaker in the song will probably continue to search for a way to express themselves in socially acceptable ways.

i think popopo could also fit kabukimono in that it's a song about an alien who travels from planet to planet in hopes of finding a home and a friend, but no one accepts or wants him so he is constantly shunned and lonesome. thus he is a "shooting star sinking in the spacey, black tar" with "hopes and dreams in teardrops," which are lines that fit kabukimono so much!