How does Makoto's aunt knows about time-leaping?

Makoto's aunt knows about Time-Leaping because she sinabi that she did it when she was younger as a teenager ^^

Because Makoto's aunt is also time leaping.

her aunt is the main carecter in the book , tv ipakita and live action movies! she accidentally acquires the ability to time travel, i dont know how because i have only seen this movie!

The aunt IS Makato. Think about it, she promised Chikari no matter what she would keep the painting alive so he could see it in his era. The aunt is always working on a single painting. No one of the present araw can time leap apart from Makato despite her aunt saying everyone could do it. So, the Aunt is Makato's future person who eventually lived until time leaping was invented, Chikari wasn't born yet so she went back to her childhood to fix the painting.