Warning: spoilers ahead.
In all honesty, I really enjoyed the second season more than the first one. Probably due to how Dazai's character is explored more thoroughly here, regarding his Port Mafia past and everything. Oh, and Oda Sakunosuke? I am in love with you and I will always have you in my heart. Although Odasaku only appeared for 4 episodes, I was able to grow an attachment to that man, as well as the friendship he shared with Dazai. In a workplace where you really can't distinguish friend from foe, you're really into suicide and are a dark and lonely genius, having someone you can actually trust sincerely as a friend is heartwarming.
It hurt me both physically and mentally when Dazai ran to Oda's dying body. Oda tells Dazai that the world isn't all black and white, that good and bad aren't as simple as that. They're all grey -- they all somehow end up doing rather dirty work to chase a goal. Dazai listens to Oda, his only real friend during his time in the Port Mafia, and Oda tells him how it'd at least be better for him if he were to join the side which saves people. So, in regards to his friend's last dying wish and words, Dazai ends up leaving the Port Mafia.
He joins the Armed Detective Agency, and his appearance visibly softens. From going all black to having a light blue undershirt and a brown trenchcoat. Although I do think that I like Dazai's Port Mafia outfit more compared to his ADA outfit, I prefer his current personality and beliefs. He has always been a dark and lonely genius, and probably still is, but his view on life is slightly more hopeful and 'light'. It's not exactly easy to describe, but I just like how Dazai is in the present, as annoying and unpredictable he may be at times.
Dazai and Chuuya's partnership is also something I liked -- frenemies that trust each other with their lives. Although they probably never explicitly said anything about it, they'll always have each other's backs, and both of them know each other like each of the back of their hands, and that is exactly why Chuuya is 'annoyed' at Dazai. Nevertheless, their teamwork is great.
The fight between ADA and Port Mafia becoming them allying against The Guild also highlighted how treacherous people can be, and it is basically part of human nature. You can't believe everything you see or hear, and you can never take anything at face value. There is seemingly always a reason behind something. Human intentions are impure, and that is basically what makes Dazai up. He is a sickening, impure genius, whose intentions are rather unclear at times, but he is Dazai -- the genius that has successfully made everyone fall in love with him.
I don't know what I'm ramblng about anymore. I just love Dazai and the plot is pretty good.
Honestly, I didn't want to start Bungou Stray Dogs at first as I felt like it was rather overhyped, but I was proven wrong when I actually gave it a shot. I wasn't really aware what it was all about, but after finding out this was actually seinen, I was intrigued. I love animes that tackle rather political and psychological themes. Characters like Dazai are the ones who pull me into the story as well (see: Lelouch from Code Geass and Guren from Owari no Seraph). They are just great.