Sasaki Isaburou commands the Mimawarigumi, a role loosely inspired by the real historical figure Sasaki Tadasaburo. Born as the main heir to the elite Sasaki samurai clan, he's also the half-brother of Sasaki Tetsunosuke.
There's a stark contrast between how he comes across in person versus through text. Over email and cellphone, he's a different person—insisting people call him Sabu-chan and admitting he doesn't have many friends. Since he struggles to express himself verbally, he relies heavily on texting as his main way of communicating. He's also pretty fixated on making sure everyone knows how elite his unit is.
When it comes to his subordinates, Isaburou places absolute trust in Nobume's abilities as an assassin and her loyalty to the Mimawarigumi. Fans often note that he knows her surprisingly well; he's fully aware of her donut obsession and doesn't hesitate to use it as a reward for jobs well done.
Content compiled by AnimeList.moe from publicly available sources.