Hagane-kin (Literally meaning "Steel Muscle") is a powerful technique created by Tosen, it's an ability that allows him to highten his physical stregth greatly using a certain method. With his control over his moleculs and cells and his skill with Life Return, Tosen can weaken and slightly damage his muscle's tissue, after doing so Tosen would use a certain technique called The Transcendent Mind in conjuction with Life Return to greatly excelerate his healing, completely healing his damaged muscle's tissue and making it stronger then it was before giving Tosen a higher level of strength. After repeated use Tosen can gain monstrous and superhuman strength and becomes very bulky. Using Life Return he can return to his normal state if he wishes to.