SarinPoison

So I'm not done with the series yet, but I've read the 20 chapters free on Lezhin.com and omg I couldn't look away.  The basic story is that a man in a sucky situation gets his by a car, but his will to live planted him into the body of a boy who tried committing suicide because of the intense bullying he received.  The man who is an absolute badass decides to stand up for himself in this new body and life while trying to figure out what happened.  Along the way he runs into an old friend of his who sees who he really is despite his new body.

It's a really good manhwa and really addicting.  The characters are believable as far as they're fleshed out (I don't know what's the deal with the brother yet), but they're like normal teenagers and young adults in that they won't tell you exactly what they're thinking.  The art is really good with showing emotion and injuries.  Definitely a must read.