I'm always pairing these two. I've even got a silly idea for an S-Support for them (this would take place during the final month of any route).
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Caspar finds Hilda in the library on top of a ladder and calls out to her. This startles Hilda, causing her to fall and for Caspar to run over to catch her. The two end up in a heap on the floor and, somehow, Caspar ends up getting a handful of one of Hilda's ample breasts. Caspar freaks out as he apologizes to Hilda, but Hilda doesn't really mind, and takes the opportunity to spell out to him that she REALLY likes him. She then laments that she's finally found something that's going to end up tying her down. Dense as always, Caspar asks what it is, so Hilda spells out to him that it's him.