The movie follows a 4-year old boy who is struggling to cope with the arrival of a little sister in the family until things turn magical. A mysterious garden in the backyard of the boy's home becomes a gateway allowing the child to travel back in time and encounter his mother as a little girl and his great-grandfather as a young man. These fantasy-filled adventures allow the child to change his perspective and help him become the big brother he was meant to be.
When Mirai and Kun are looking at their family history, they find that the reason their mother currently prefers dogs to cats is because she saw a cat kill a baby bird. She hold's the bird's corpse and its blood is visible.
No but there are at least two occasions where the idea of toys being thrown away is threatened (which did at least hit me a bit as someone this actually happened to)
The entire movie centers around a toddler adjusting to life with a baby sister. (Side note: please look at the damn title before putting stuff from Future Diary in here!…just saying you ever noticed that it contains only one word and was released in 2018?)
It's not prominent, as this is a kid's movie. However, when Mirai and Kun look back on their family history: Mirai's and Kun's mother holds a baby bird's corpse, and its blood is visible. Mirai's and Kun's great-grandfather, during a bombing, is shown with a large, fresh wound in his leg.