For an MC who belongs to a Assassin's Family and Mastered almost everykind of Assassination Techniques, he seems to be quite oblivious.
I mean, he first escapes from his family when a Monster outbreak occurs in Tokyo. And after escaping the city, he nonchalantly enters a market to buy stuff and even get surprised to see the owner beheaded and monsters roaming around.
I mean if a person escapes from a monster (or zombie) outbreak, they would try to be cautious about their surroundings as much as possible, even if people around won't believe what he says (like the reason he didn't contact police on seeing the monsters).
Next, when he meets the Elf girl, he tries to immediately flirt with her, which is odd given that she doesn't really looks normal human, and Elf's are a common category of beings that appear regularly in all types of franchises (so he should have been able to guess more easily).
Also he tries to talk about Weapons Law to the Elf girl, when he knows what's going on in Tokyo. I mean why talk about laws and stuff when weird things are happening nearby. It's like suddenly Japan is thrown into a War and people are dying, but MC is still talking about weapon restrictions laws and what shouldn't be owned by common public.