Volatile: Liable to change rapidly and unpredictably, especially for the worse.

What is the price of your Dream? Izuku Midoriya told himself that he would do anything to be a hero. With the Contract made between him and the newborn Devil, he will find out just how far the definition of 'anything' can go. For you must never forget, you may always negotiate the price of the deal. But whether you rejoice or regret is entirely up to you.

Denji is a very poor kid from the country who was going to die because his parent left him nothing but debt. However, he meets a weird dog which he names Pochita, and together they do all sorts of jobs. As time goes by he discovers about the existence of Devils among people and a mysterious girl named Makima tell Denji to enroll UA to help kill all the higher-up devils out there.

Tekijugu also known as the insect demon from chainsaw man was killed brutally by makima. however despite teki died his other half manage to survive causing him to flee from the building. while in his insect form he flie's out of japan and tries to find a new host until suddenly for some reason he ended up at an apartment with a human teenager sleeping inside causing him to be him.

Izuku Midoriya never gets the chance to impress All Might and inherit One For All. Instead, a devil listens to his dreams of becoming a hero and decides to make a contract. Make way for The Chainsaw Hero, Deku!

This isn't the MHA/CSM crossover fanfic you expected for :)