"Strong friendship or devoted love"

Dazai Osamu and Nahakara Chuya met when they were only 15 years old. They were friends and are still friends. Now inseparable friends. They're like a Cat and a Dog. Sometimes they quarrel, and then immediately measure up. They are one and the same, like inseparable water. And so three years have passed since their strong friendship. They obviously grew up during this time and they were already almost 18-19 and a half years old.
Also at this young age, they were entrusted with a particularly important and serious task from the Port Mafia. It had to be completed at a certain time-at night, when it was very dark. And refusals were not accepted at all.
After completing the task, Chuya had to go to another city for four years on business. And Dazai can't stay alone alone without his best friend, partner Chewie, who could at any moment become his shield and save him from various bad situations, thereby helping him.
In order not to lose these four years, Dazai decided to find a girlfriend so that it would not be so lonely and boring. He soon became friends with a young girl Naomi, who worked in an "Armed Detective Agency", and then he married her and began to live with her...