At the start, the MC was asked to fix something for his classmate. It was a old recorder or something, I forgot, but on his way home, he sees some guy jump in front of a train.
The MC then gained that guy's memories and found out the guy was from an old clan. The MC was then able to fix the object with the new knowledge.
He was able to participate in a tournament/test or whatever later on and made weapons and sold them for points during the test. In the test, some guy had a strengthening drug and a monster took it and used it. That monster ended up "crippling" the MC.
The college that was planning on recruiting him ended up changing their minds. He dropped out of his school because they wanted to kick him out, not knowing he got better.
Later on, he joins this one college that was about physical strength or whatever. He ends up dating someone there. That's about all I can remember.