[2]: I find this line strange, because I can't quite understand what it means in bringing up diurnal (which is the opposite of nocturnal. Most owls are active at night, diurnal ones are active in the day) owls here. But, after some contemplating, I think it has to do with how most owls are nocturnal. Japan in specific doesn't commonly have any diurnal owls (http://www.raptors-international.org/book/raptors_in_the_modern_world/Brazil_Yamamoto_1989_389-402.pdf). In this sense, if an owl were to be nocturnal in Japan, they would stand out quite a lot. With that in mind, you could also say that if a nocturnal owl tried to change its nature and become diurnal, it would be fully out of its element. Owls have evolved in many ways to suit being a largely nocturnal series, so while diurnal owls do exist, they're not common and likely don't have the ability to take full advantage of their biological abilities (like night vision, for example). While this note is purely speculative, I wanted to give my input due to the... Really odd nature of comparing someone to a diurnal owl. I believe it's essentially a commentary like, "your abilities have no use here" or "you're out of your element" which ties back nicely to the scenario Tsukasa imagines in DDFL (as this is seemingly the basis for the entirety of Sayonara Tengoku).