Princes, Take Up the Brush! is the nineteenth chapter of the Oushitsu Kyoushi Heine manga.
Heine tells the princes that today's subject will be on art, and that they will be drawing a portrait of their sister Adele. The princes are hesitant as none of them are artistic, but when they hear that the one who drew the best portrait will have their piece hung in the art museum for a week, they are much more enthusiastic. However, it quickly turns out that all the princes, with the possible exception of Licht, have no talent at all for art. Leonhard in particular is discouraged by this, and would have given up if not for Heine revealing he's also terrible at art by drawing his own portrait of Adele. Leonhard decides not to give up yet, and everyone proceeds to finish their portraits. To their surprise, Adele loves all of them, but chooses Heine's portrait as her favorite. It ended up hanging in the art museum, where the art critics, afraid of being seen as fools, heap praise on it.