Junpei is the worst one in here. Worse than Rina.
At least Rina has the excuse of her poor mental health and abusive relationship. And now will have to fight to survive as a single mother. Junpei is the one who almost got away scot free with a loving family and a better, more convenient job, after having ruined the lives of everyone around him.
And yeah, don't tell me that it would have been fine because he regretted it. The retard has been lying to the last moment with the stupidly keeping contact with Rina. He had the gall to get angry at Azu for some alleged revenge sex she had every right to return sevenfold. When you are the biggest asshole in a story with two literal sociopaths, that's not great.
And you know who ended up having to mop up his mess? Not him, that's for sure. Hell, I'm glad Rina exposed him. Deserves worse than that.