Ango Sakaguchi (坂口 安吾, Sakaguchi Ango?) is a government worker from the Special Division for Unusual Powers whose ability is Discourse on Decadence. He was close friends with Sakunosuke Oda and Osamu Dazai four years ago.
He is a tall man with short, dark hair that has the bangs cut so they regularly show his eyebrows, and lightly-colored eyes behind circular framed glasses (though his hair is portrayed as somewhat messier in the anime). His most notable feature is a mole above his lip on the left side of his face.
His normal attire consists of a pale brown double-breasted coat which is buttoned to the left, covering a tab collared shirt with a kobicha brown tie. His pants are the same color as his coat, with his shoes being roughly the same color as his tie.
For the most part, Ango is a composed, calm young man, showing more restraint than Osamu Dazai and more discipline than Oda Sakunosuke. Although he values both as genuine friends, he strongly believes that Dazai needs someone to keep him from acting out as much as he does.
Despite being a spy for the Special Division for Unusual Powers, Ango takes his role as their informant seriously. This includes his efforts recording the lives of deceased mafiosi after the Dragon's Head Rush incident. He records everything from their background to family lives, and makes sure all close relatives are aware of their deaths, but is careful not to let on their connections to Port Mafia. As such, Ango values life a great deal.
When his true intentions are revealed in Bar Lupin, Ango struggles to remedy the strain and tension that arises between him and the other two. However, after being shut down by both Dazai and Oda, Ango respectfully withdraws.
Even after their fallout, Ango continues to respect Dazai, albeit appears even more exhausted by Dazai's theatrics and conniving ways than ever before.
Discourse on Decadence (堕落論, Daraku-ron?) is an ability that allows the user to read the memories left in things, a memory extraction ability.
Despite being useful, this ability can put a considerable amount of mental strain if the user had yet accustomed to it. Ango confirmed this had happened in the past when his brain temporarily surrendered consciousness in order to sort an influx of large information gained from his ability. This ability may also work with humans as seen when Ango offered to read the information sent by Sigma towards Atsushi Nakajima in order to figure out Kamui's location.
Not much is known about his past but it is revealed in the second light novel (Dazai Osamu and the Dark Era) that Ango once worked as Port Mafia's Intelligence Agent, but it was under the Government's orders to spy the mafia's activities. During his time working as an intelligence agent under for the Port Mafia, he also became an agent for Mimic under Mori Ougai's orders.
It was later believed that Ango is not a mere government worker, but instead, the leader of The Seventh Agency, as cited by Mushitaro Oguri, which Ango denied upon his questioning, telling that it was a lie told by Fyodor Dostoevsky.
- (to Osamu Dazai and Sakunosuke Oda) "The death of a person is not just some number. Every one of their lives must have some meaning."
- Despite being close to both Odasaku and Dazai in the original series, Ango makes no appearance in BEAST - White Akutagawa, Black Atsushi, nor is there any mention of him.
- His real-life counterpart Ango Sakaguchi was born with the name Heigo Sakaguchi (坂口 炳五, Sakaguchi Heigo?). Ango is often grouped together along with Osamu Dazai and Sakunosuke Oda under the buraiha literary movement. This groupment is often alluded to in the series, especially with the trio's nightly meetup in Bar Lupin.