Shut-in Reincarnated as Gorgeous 17-years-old Girl

A fatty shut-in, Kazuki Katsuhisha died in an accident when he went out of his home for the first time in six months. He met with this bad luck after saving a child too. Feeling wronged, he refused to go to the afterlife, and then found himself reincarnated into someone else's body. However, the body was of a gorgeous 17-year-old girl. What should a guy do in this situation? I'm posting this story on Royal Road L as well under the same author name, Walraevens