The incredible way Harukawa-sensei conveys the character's emotional mindset with just their eyes is hard to adapt in the anime. Dazai's eyes are the perfect example to show how he is torn between his past and his present self. When we first met him, his eyes were neutral black,
which applies for most of the other characters as well.
The anime tries hard to show the dramatic emotional changes of the characters by usually adding those shiny “pling-things” at the outside of the iris.
The anime tries hard to show the dramatic emotional changes of the characters by usually adding those shiny “pling-things” at the outside of the iris.
When Dazai is acting aligned with Odasaku’s last wish, he eyes brighten up immensely.
That's how we see him when he mentions the ADA (left) and also when he made the deal with Kouyou regarding Kyouka (right).
That's how we see him when he mentions the ADA (left) and also when he made the deal with Kouyou regarding Kyouka (right).
The way he’s looking at our broken Atsushi in warehouse shows, that he has good intentions and that he saw something more in him from the very beginning.
It’s different from how he was looking at Akutagawa during their first encounter, but even here, where he was deep involved with the mafia, his eyes were not completely black or dull. Even though he couldn’t show it to his subordinate back then, Dazai knew why he was taking him
under his wings.
For those who claim that Dazai is merely using Atsushi: Look at how he is looking at his protegé before “earthing” him again after being possessed by Q. (enlarged for the full pic
)
For those who claim that Dazai is merely using Atsushi: Look at how he is looking at his protegé before “earthing” him again after being possessed by Q. (enlarged for the full pic

The only times our present Dazai’s eyes have these dark shades of grey are when he gets confronted with the burden of his past, e.g. when he was called a “Traitor” by Kouyou or when he was looking at Chuuya pretending to kill Q.
Speaking of which: When Dazai was after Q and their doll his eyes were bright, since he was acting in order to protect and doing good, but his last look at Q, before they left had these terrifying circled shades of greys in his eyes!
While being imprisoned with Fyodor, waiting for his bf to finally pick him up, his eyes carry everything he experienced and learned from his past up until now, but with this meaningful spark of light in his eyes. We readers can just feel his the severity of the situation.
Last, but not least: What I like the most is the fact, how bright and full of light his eyes get whenever his bickering around with Chuuya as well as Kunikida, since it shows his childishness and that genuinely feels good fooling around with them
