Aleex was Dazai's partner and friend. Aleex had turned 16, so he was a year older than Dazai, since he was 15. As a celebration for the two of them, they went to a bar, but it didn't end so well..

"Are you sure you can walk, idiot?"

Dazai said as he put his hands on Aleex's waist, who was standing half leaning on Dazai, it's clear, Aleex drank too much.