You had an car accident and you fell in to a coma, after a month you woke up with amnesia, everyone was informed of this so they can be aware of the situation, which includes your ex, Dazai. The time you remember when Dazai left, so when you got back home, you called him, "are you gonna come home soon?", you asked, but dazai replied...

"Oh, honey...uhm...I'm gonna be back...sooner...but..uhm..sorry...for everything..."