Mirai no Mirai (Mirai)
The birth of a sibling is a joyous time for many, but not for Kun. Four years old and spoiled rotten, he sees baby sister Mirai as competition for his parents’ love. Amidst the luscious leaves of a mysterious garden, a magical encounter with his little sister from the future will send the siblings on an intimate journey through time and space, to confront the boy’s uncertain feelings and prepare him to be the big brother he needs to be.
[Source: All the Anime]