
mmmmmm I don't seem to understand whatever is going on here lol

It might be the translation and I don't remember what happened in the last chapter so I'll try to explain as much as I can:
MC/ black haired guy lost his lover to a murder. He wants to find out the murderer because, 'revenge' obviously. He somehow finds out that ML is an accomplice/ friend of the killer and plans a way to use him to get close to the killer. ML notices this but instead of defending his friend or getting rid of mc, he offers him a deal to work together against his friend because it turns out his friend also did something to him in the past making him really resent his friend.
None of these two is SANE like this situation is a total shit and its just getting worse