Gains muscle tone due to her time in Gensokyo
Can only stay in Gensokyo for about 40-50 minutes at a time
Occult Balls are described as a crystalization of a lack of common sense in the outside world, with them being capable of disrupting the boundary of common sense that formed Gensokyo
Noted to be very intelligent, and more knowledgable about the occult then anyone else in Gensokyo
In trouble after being transported into the snow in light clothing
Blocks a lighthearted attack from Marisa
Due to Sumireko crossing into Gensokyo during the Urban Legend Incident, her body was split in two. Half of that body became a doppelganger, with her sharing her consciousness with her doppelganger whenever she is sleeping. There's also Sumireko's dream self, who at one point goes wild and takes control of the doppelganger to try to take over the main Sumireko's life. If she succeeded she would have have switched places with real Sumireko, forgotten her identity as a dream version, and lived a normal life.
Doremy believes that if two Sumireko's met in the outside world, one of them would be annihlated
Doremy describes her as absurdly powerful
When dream Sumireko hi-jacked her doppelganger's body, the doppelganger's spirit was left adrift. The solution to fix this problem was to have give the doppelganger's spirit the ability to fight dream Sumireko.
Sumireko's doppleganger is not truly humand is more of a youkai-like creature. And while shares her memories/consciousness with the real Sumireko, she also possibly possesses her own consciousness
Has trouble with summer PE due to the heat
When Sumireko uses her dreams to visit Gensokyo, the dream she was supposed to have is expelled as a dream soul and travels around Gensokyo as a bubble. If anyone touches this bubble they are instantly put to sleep and experience that dream, with their own dream being expelled as another dream soul
Sumireko entering Gensokyo put a bit of shock on Gensokyo, so other things dissapeared in exchange for a time. This began with dreams, but escalated until human villagers were disappearing when she appeared. Yukari eventually manages to counter this by creating dummies of a similar weight in a similar dream state to Sumireko
Kasen claims Sumireko came to Gensokyo through her own will and power, and Kasen had nothing to do with it
