I wonder if this ever explains how elves fit into this world. Like are they supposed to be mythical and nobody knows about them except Takeshi?
Because that's the only way the central conceit of a lot of the comedy (that everyone thinks Ellie is way younger because they don't know she's an elf and ages slower) works.
Otherwise that "cover your ears!" bit in the first chapter doesn't look like him trying to keep her secret. Instead it looks like that crappy "don't stand out! I need you to be normal!" trope that pervades some manga.