So it didn't occur to him that it was exactly what it was?
Just how brain-dead do you have to be to not realise that two people under one umbrella = shared umbrella?
Would it baffle him to learn that water is wet?
Those tiny, shitty little umbrellas are rather bad for sharing though.
He thinks: "what will she do if someone sees us?"
Holy mackerel, how dense. Dude she DOESN'T CARE if someone sees you together. My lord, I wish I lived in this world just so I could smack some sense into this knucklehead.
In short, I love this manga.