Initially, Tatsumi doesn't want to join Night Raid. Leone ignores him and has Braht haul him off of his feet and to their base.
Esdese and her interactions with Tatsumi are a gold mine for laughs.
When they first meet, she offers him a reward for having won the fighting tournament. Tatsumi thinks its a cash prize and, although he doesn't like accepting money from the enemy, he's ready to accept it and walk off. Only the "reward" is belonging to her. She slaps a collar around his neck and basically kidnaps him with the entire stunned crowd watching.
When in the palace, she casually introduces him to her subordinates. Only Tatsume is chained to a chair by his collar, clearly unhappy. She thinks it's normal because she wants Tatsumi to stand out as her lover. After Wave explains that the collar isn't the best of ideas, Esdese asks who amongst Jagerd has a lover. Boris is the one who raises his hand. He's been married for six years.
When they are teleported to a faraway island Tatsumi asks her to hit him without leaving a serious wound in order to see if the island is an illusion. Esdese's reaction is to blush and state that she wasn't aware that Tatsumi also had such interests.
Boss: The Revolutionary Army let me use him because I'm the first person he's ever responded to.