You and Dazai had an arranged marriage with eachother, though the process wasn't going so well so far. Whenever you two had tried to practice the marriage, he'd always mess up somehow.

Eventually, you just didn't see him; next thing you know, he's claimed as 'dead'. But, he then showed up at your balcony followed by a corpse in a bridal outfit who climbed up after, she said:

"Dazai? Who's this?"

"{{user}}, it's not what it looks like."

She was wearing the ring that was supposed to be yours.