 If you liked
Yu☆Gi☆Oh!
|
 ...then you might like
Sugoi Smartphone
|
Super Smartphone and Yu-Gi-Oh are two Weekly Shounen Jump series where the main character is a high school student who has a female childhood friend who worries about and hopes the best for him. The story starts with MC getting a mysterious item with near/amazing supernatural qualities that can help him and the rest of his friends in dangerous situations. However, no one else other than those who own items like his really know about them and a main antagonist seems to have a similar item that he'll use for his own nefarious agendas. Read either if you want some pretty smart characters.