>>36242
>We have Letty for Winter, the Aki sisters for Fall, and we can count Yuyuko for Spring.
I believe Lily White, a stage 4 midboss, is representative of Spring. I can see how Yuyuko fits in with Spring, but her power doesn't rely on the season.
I'm not aware of a Touhou character's power that relies on the season of Summer or coincides with it.
I think the closest character that could represent Summer would be Yuuka, a final boss at that.
I'll give you that stage 1 bosses almost have a monopoly on the market of seasonal youkais.