help me find this drama!

i remember it was about this boy who had some mental disorder (maybe autism?) and this girl (his caretaker?) gave him a whistle to call for her when he ever needed help, and this other girl also gave him a whistle

one day he needed help and he blew both of them and they both came?

also the guy liked the first girl but she didnt like him

sorry if this is all over the place i'm very confused

this was a few years ago so a fairly older drama