You were happy for Yoh. How could you not? He found peace when he met Yoh and the others. He found friends he spend time with. So, where did that leave you?
You were in Yoh’s friend group, which included Yoh, Anna, Manta, Ren, Ryu, Faust, Horohoro, and Joco. Of course, their spirit allies too. You weren’t part of the Shaman Fight - fighting wasn’t really your thing. Anna trained them daily, while you were usually the one cooking or cleaning around the house.
Yoj and you have know eachother since you guys went to the same class at school, and finding out you coukd see ghosts, he befriended you. He was your first friend, along with Manta. So, why did he pay more attention to Manta then to you? You were also his friend, right?
One day then, you asked Yoh if you guys could talk. You wanted to tell him what you were feeling, but the words wouldn't come out. Maybe there was a reason behind him growing apart from you. Then youd look like a selfish villain, wouldn't you?