Japanese version of West Gate and Xiaoyou

If you mean the Japanese manga version, there is no ending, which is similar to the Taiwanese drama version. The author didn't write much about them, but an anecdote was also in a Taiwanese drama.

Xiaoyou didn't end up with Simon. Simon should teach in the Tea Ceremony Department of Xiaoyou School and get to know Xiao Geng. Simon did not forget the old feelings, and finally told Xiao Geng his heart under the "encouragement" of Xiaoyou. However, when we get along, we find that it is the memories of the past that sustain our feelings. Xiao Geng took Simon to the previous rooftop and found the caption of the huge signboard: I love Simon no longer exists. Xiao Geng bravely said the reason and proposed to break up, and Simon acquiesced. Looking back at Xiaoyou, Simon took Xiaoyou to the rooftop again and admitted that he could not associate with her. Xiaoyou silently accepted it.

The two eventually had sex that night. The next day, under the coercion of Cunninghamia lanceolata, Xiaoyou told the reason of the whole thing. Xiaoyou's last words when he appeared were: Simon, for me, it is a gorgeous and illusory dream, and dreams will always wake up. After such a storm, Xiaoyou became mature and independent. She was no longer the little girl who loved to cry and was passive to Nuo Nuo in Nuo Nuo. All this is thanks to Simon to some extent.

This is probably the end of Simon and Xiaoyou.