There have been leaks about Genshin Impact's future characters coming out from the Sumeru region during and after Genshin Impact 3.0. While there isn't a whole bunch of information yet, bits and pieces about characters are being leaked. Su Expy is one of these characters that is allegedly playable during the Version 3.0 content.
A lot of these leaks about Sumeru and its characters are coming from what the Genshin Impact community calls "reliable" leakers. Reliable in this sense means that there is typically some element of truth to their leaks, and they are proven correct more often than not. However, no Genshin Impact 3.0 leaks should be taken completely seriously or as undeniable truth, and players should wait for official announcements from HoYoverse about what is real and what isn't.
From what leakers have shown, there are a lot of new playable characters that are lined up to be released in Sumeru. Su Expy is one of these characters, and more information has been leaked about him than some other characters. Some parts of his design and his personality have been determined so far - ahead of Genshin Impact 3.0 coming out later this summer.
Genshin Impact: Is Su Expy Really Playable In 3.0?
Characteristics about Su Expy have been allegedly leaked on Reddit. He is a tall male character in Genshin Impact like Zhongli and Ayato, and also has a similar face structure to them. He has been leaked to wear a black collared sleeveless shirt, with an overcoat on top of it that falls diagonally from his right shoulder to his left waist. His shirt is somewhat translucent, and there is a lot of teal in his design. His hair is grey with long side-swept bangs and green accents. It has been noted by leakers that Su Expy bears a resemblance to the character Su from Honkai Impact, meaning that their designs will likely be very similar, like how in Genshin Impact Yae Miko was based on Yae Sakura.
The only thing revealed about Su Expy's personality is that he is a scholar from Sumeru. His Element, weapon, and rarity are all unknown so far, so players will have to be patient for more leaks. It is possible that Su Expy is Dendro based on the bits of teal and green in his design, but colors in design do not always point out a character's Element, and a few other Dendro characters coming to Genshin Impact have been leaked already: Tighnari, Collei, and Yaoyao. There have been leaks that a 5-star Cryo character is releasing in Genshin Impact 3.0, so Su Expy could take that spot, but players won't know for absolute certain until HoYoverse begins to reveal these characters themselves.