Hi, I'll write it here because the text I translated is very long and I can't insert it when I reply to the comments. I'll also try to explain it more clearly:
There are no two worlds in this story - everything happens in one universe. As I said, Ayanokōji from the White Room died in 2022 when he was 24 years old. But in 2024, he suddenly woke up in the body of a 17-year-old boy who has the same name and appearance, but who looks a little younger.
As for Ichika, she is now 16 years old, which means she is only 10 years younger than Ayanokōji from the White Room. If Ayanokōji from the White Room were alive, he would be 26 now. When he was 14, he destroyed the White Room, and Ichika was only 4 years old at that time, since the age difference between them is 10 years.