The Tenrai Musei(天国衝撃的なボイド魂, Lit. "Heaven Shocking Null Soul") is decribed by Rasetsu as "a flowing world of mystery. Morphing hyper dimension gels. Speed Heaven, the source of my speed". Tenrai Musei is the ultimate force of speed, making the user superlatively fast with absolute movements.
Tenrai Musei is an energy field which grants those who are aware of it and that can tap into it absolute speed. Merging with it causes supreme omnipresence through speed alone, something which Rasetsu has achieved.