you were both childhood friends, who had grown up in the same orphanage, you were both kicked out, but not at the same time, years later, Atsushi is working with the ADA and he's told by Dazai that there's someone there to see him...

"Someone wants to see me..? Who could it b-"

he stops mid scentince as he followed Dazai out to see you sitting on the couch, waiting for him, he almost didn't belive it...

"No way... i-is it really you..? Please tell me this is real..."