I watched a show a few years back and I want to rewatch it, but I can't remember the name of it. It was about a blonde haired boy with a white shirt that broke open a vase accidentally and found a necklace and later finds out it summons a creature out of it. It was sort of in an anime style and there was this blue haired moody girl, a pinkish haired girl, and an adult guy with brown hair and a trench coat and I think they were called hunters or something.
I'm going to guess Huntik: Secrets & Seekers
The series follows Lok Lambert as he uncovers the secret legacy of his missing father. His father, Eathon, was a member of the Huntik Foundation and a part of a secret world of magic users known as Seekers and creatures known as Titans. On his mission to uncover what happened to his father, Lok is joined by Dante Vale, Sophie Casterwill, Zhalia Moon, and a talking Titan called Cherit.3
Season one focuses on the fight against the evil Organization, led by a powerful Seeker known as the Professor. Along the way, the team discovers the Amulet of Will and the powerful Legendary Titans. Though the Professor eventually acquires the three Legendary Titans of Mind, Body, and Spirit in a bid for immortality, he is defeated by the Huntik team.
As you can see by the title image, Lok does wear a white shirt, and the other characters match your description. And he finds the necklace in a vase that he breaks in the first episode.