It's the Forest of Fireflies by Mr. Midorikawa Yuki who is very popular in Japan.
It was also changed into animation or something.
Always liked it
So I wrote it myself
Six-year-old Ying lost her way in the mountains and met Jin, who "must never be touched by humans." From then on, Yingying would come to see Akin every summer. As time passed, their relationship changed, but there was always an insurmountable gap between them.
At the end, the two finally hugged each other.
A once in a lifetime hug, a once in a lifetime love.
Conception: