Kyūsaku Yumeno/Synopsis

The Guild Arc
Ōgai Mori releases Q during the three-way conflict, using them as part of the bait scheme to drag both the Guild and Armed Detective Agency down. They board the same train as Kirako Haruno and Naomi Tanizaki. The girls run into them in one of the train cars and apologize, to which Q insists they're the one who should say sorry. The girls later introduce Q to Atsushi once he arrives to retrieve them. Q intentionally bumps into Atsushi and shows off the gruesome razors piercing their skin.

Q's doll laughs maniacally, floating over their head, and tears its own head in half. Q entertains themselves watching Dogra Magra work on Atsushi, making him hallucinate Naomi and Kirako as the ones being affected and attacking him. By the time Dazai stops Atsushi and nullifies Dogra Magra, Q reboards the train just as it starts up, and comments how Dazai's new friends are easy to break. Q says this is fine, as they'll save Dazai's breaking for last, intent on breaking everything and forcing Dazai to go through the worst pain imaginable. According to Dazai, confining Q turned out to be a harrowing task, leading to a massive death count for the Port Mafia. At the end of his patience, Dazai declares he'll tear Q's heart out the next time they meet. Q smiles and laughs, shutting the train door and escaping.

A week after Francis Scott Key Fitzgerald abducts Atsushi, Q continues to enjoy life outside confinement. They wonder who else they can "play" with, the meaning ambiguous, but recalls that Mori told them not to "play" with anyone until finishing their work even though they're bored. Q locates Howard Phillips Lovecraft, asking him to play. Attempting to humor them, Lovecraft tries mimicking balloon animals, but naturally, his tentacles merely make a grotesque display that grosses Q out. Q decides to harm themselves on Lovecraft, telling him to show them how insane they get. His body contorting, Lovecraft reveals his true form to Q, terrifying them and leading to their abduction.

Locked away in an abandoned building by Steinbeck, Q suffers relentless torture and pain thanks to Steinbeck's Grapes of Wrath, which writhes through Q's body. The agony drives Q's state of mind to dangerously unstable levels. Grapes of Wrath connect Q's pain and the 'pain' trees feel when harmed by citizens, essentially making their pains one and the same. As such, anyone harming trees and other flora receives Q's curse. At their breaking point, Q bursts into tears, lamenting their misery. They never asked for their ability, and don't understand why bad things always happen to them. Steinbeck indifferently explains that Q suffers simply because they were born, and even though God exists, God doesn't love Q. The exchange ultimately breaks Q, who activates Dogra Magra's curse.

After Atsushi recovers the doll from Fitzgerald and has Dazai nullify the ability, Q apparently loses consciousness, with Lovecraft and Steinbeck guarding them, aware the Port Mafia and Armed Detective Agency will come to rescue them. In the aftermath, the Port Mafia suffered 18 deaths and over 100 other causalities related to sub-organizations. Assigned to save them, Dazai and Chūya revive their Twin Dark status. Once he reaches Q, Dazai threatens to kill them, but Chūya tells him to go through with it. holding a grudge against the deaths Q's ability causes. Dazai bluffs, as for as long as Q stays with the Port Mafia, no one can afford to kill Dazai - making Q insurance for Dazai's life. Chūya recovers Q, but Lovecraft attacks. Not until Dazai and Chūya defeat Lovecraft is Q returned to the Port Mafia. They have not been seen since.