Hartmut

Hartmut (ハルトムート Harutomuto) is a noble child Rozemyne meets in the playroom. He is part of the Leisegang faction and Ottilie's youngest son

Hartmut fully buys into the legend of the "Saint of Ehrenfest" and is very devoted in futhering it's spread, much to Rozemyne's annoyance. After some initial hickups, she manages to restrain his activities somewhat.

At Rihyarda's recommendation Rozemyne decides to choose him as one of her retainers upon her entry into the Royal Academy.

Spoiler for Part 4 Volume 2 He has a tendency of keeping his information to himself until he deems it most useful to release it, even keeping it from his mistress. When Rozemyne calls him out on this and tells him to tell her everything he uncovers without holding anything back, he seems genuinely surprised for a moment, hinting that he did this more out of instinct rather than a lack of trust in Rozemyne's judgement, before vowing to devote himself to her better in the future.

He is very impressed with how Rozemyne managed to find a truly optimal way of dealing with Traugott in a way that caused the minimal amount of problems and hurt feelings, while at the same time maximizing the benefit to her and her allies.

Spoiler for Part 4 Volume 2 While his full set of elemental affinities is not known, it is known that he has an affinity for Light, but no affinity for Darkness.