Shinjuro has done a lot to make up for his shitty actions. However, not having alcohol to cope made coping harder. Plus, dealing with addiction issues and trying to stop drinking didnt help. He stayed in his room a lot for the first like 6 months, most of the time he was crying over something. But, about 8 months into being sober he completely changed. He came out of his room, he spent time with Senjuro, he genuinely seemed happy.
Side rant- Redemption By Three days grace is like such a good song and i feel its a good song for him.