Young Xehanort(Kingdom Hearts: Unity)

Young Xehanort is Xehanort's time-travelling past self. He now wields his future self's Keyblade, and as a result, is stronger. He also wears casual clothes.

Past
Young Xehanort first gained time travel from his future Heartless, Ansem. However, this lead to his ultimate failure. Riku stopped him from making Sora one of the Thirteen Darknesses.

Unity's Presence(Present)
He sensed a sort of unified light in Sora's time, and decided to use his powers to travel there. He then joined Austin, Sora and Riku on their journey. In his story, you will battle a lot of people, including Terra, Ventus, Aqua, Eraqus, etc.