Sweet Sixteen (2016)

Both are dark and twisted tales where the males leads are obsessed. The ML's are also younger than the FL.

there is a boy who is younger than the girl and loved her since childhood and the boys are so cute exo's kris wu

Similar in the fact that FL has a great relationship with 1 ML & a second ML, who is so obsessed, thinks stalking is protecting....I guess it is all in how you stalk.....