Age: About 5 or 6 years
Family: Natsuki Kazuyo (mother)
Natsuki Rin (sister)
Natsuki Yu (twins brother)
Ai and her brother Yu are twins and Rin's younger siblings. Ai and Yu are so naughty that they always trouble Rin. But they're mostly like normal little kids who want to have fun and are curious about things. Despite being a real pain to Rin, the siblings share a strong bond and the twins' big sister will do all in her power to protect them. Ai and Yu get very well along with Nozomi despite annoying her too, which probably is because of her childishness and sister-like relationship with Rin.