Mugen" (Demon Slayer: Hashira Training Arc OP)

"Mugen" is built like a fortress — heavy, deliberate, and seemingly impervious to compromise. MY FIRST STORY's melodic rock instincts collide head-on with HYDE's three-decade reservoir of visual-kei gravitas, producing a collaboration that honors both artists without flattening either into the other. The guitar work is muscular and chromatic, favoring wide intervallic leaps that create a feeling of physical momentum, while the rhythm section drives with a precision that suggests training rather than spontaneity — appropriate for the Hashira arc's themes of discipline and transcendence through suffering. HYDE's voice carries the worn authority of someone who has genuinely lived inside darkness and emerged with something valuable; his contributions ground the track's theatrical impulses in flesh and consequence. MY FIRST STORY's vocalist brings youthful urgency that creates productive tension against HYDE's weathered delivery, the two voices embodying different stages of the same warrior's journey. Lyrically the song circles around the concept of "infinity" — not as abstract mathematics but as the internal experience of pushing beyond human limits until limits cease to matter. It plays ideally at full volume, preferably during exercise or any moment demanding concentrated willpower.