Bound by a Secret Pact

16yo Leo Blake, a scorned D-rank Blake outcast with failing heart, has only adoptive mom Sophia. Betrayed Shadow Clan Selwyn bonds with him in symbiosis, granting power. Leo shatters the unbreakable stone, earns respect. When Zeno attacks the city, Leo risks death for full symbiosis, uses Star Fall Slash to save all. Selwyn departs; Leo returns to Sophia.