It depends I guess, I think they are childhood friends and for them doesn't click because they simply never thought about it.
Some authors made childhood friends from kids that were besties for a week, some for years with a separation of 10 years or eve less, in short, it depends on what the god of the manga decides.
Is one of the reasons that made me dislike Nisekoi, even known as Clichekoi as it had nothing original, the MC remembered his promise perfectly but had totally forgot the face and every feature of his beloved childhood crush, and was mixed about who it could be between like 3 or 4 girls that had nothing in common with each other, and it had happened just some years before, not even a long period of time.
I think the gorilla was the one in the photo in the end, of the fuck you forget the girl you liked was the only blondie you had ever meet?
I don't knwo because I got tired of it and when the author made so he tried to fix the photo holder and it got thrown away I did the same.