"Met her in the library"? nahh I think I see what's going on here... You read some random manga and got hooked on one of the waifus, didn't you?! Your bro can't see her because she isn't real, am I right?!
There's adolescence syndrome in this anime which affects everyone in their adolescence so the girl in the picture mai get invisible to everyone except the guy in the picture
https://allmanga.to/search-anime?tr=sub&cty=ALL
Bookmark this site, i don't think it has ads but i may be incorrect.
It is kinda wonky but you can change some of the settings which will make it not as hard to navigate through.