Denji is a teenager who lives his life as a Devil Hunter.

Aiming to pay off the debt he inherited from his father, he starts hunting devils for the yakuza with his buddy Pochita, a "Chainsaw Devil", while living a tragically poor life.

Just when things seem like they couldn't get any worse, Denji gets betrayed and killed by the yakuza. As Denji starts passing out, he hears someone calling from inside his head...
Here's the deal. I'll give you my heart...
...دعنا نتعاقد. سأعطيك قلبي
Wir schließen einen Pakt.
Este será un contrato entre nosotros.
Te daré mi corazón.
Haremos un trato. Yo te daré mi corazón…
On va passer un marché.
Je t’offre mon cœur.
Esse é um acordo.
Eu vou te dar meu coração.
Мы заключили контракт.