Bonded at last.
Given the movie is about a young boy learning to accept his new infant sister, there are always going to be heartwarming moments.- The photos of Yukko as a puppy and Kun as a newborn/baby/toddler in the prologue.
- Kun in general when he's happy or excited.
- Kun's (initial) excitement at wanting to be the best big brother he can be, intent on teaching her all the fun things about the outdoors he's come to love (dragonflies and seeing shapes in the clouds).
- Kun's first glimpse of his as-yet-unnamed sister, he can only gasp and stare in amazement and offer her his thumb and she grips it, prompting her to open her eyes.
- Baby Mirai and whenever Kun looks at her with a positive expression.
- Kun running around the house as a human/dog hybrid after removing Human Yukko's tail and attaching it to his own body.
- The bond between Kun and Yukko in general since Yukko never gets any attention from anyone else.
- Kun and baby Mirai's near-identical sleeping positions.
- Kun's mother showing him her photos, especially the ones of her and her brother as kids.
- Kun trying to comfort his mother's child self, even if she is faking it.
- Kun playing with his mother's child self until they realise the extent of the resulting mess.
- Despite that their relationship was a bit rocky in the past, Kun's mother holds no ill will towards her own mother for telling her off for making a mess as a kid. Her own experience with raising Kun has taught her to be more empathetic with what her mom had to go through raising her when she was Kun's age.
- Kun's mother kissing his cheek and calling him her angel while he's asleep, he later wakes up and returns the favour by patting her head.
- The older boys at the park averting Kids Are Cruel by offering to help Kun ride his bike, and showing concern for him when he starts crying for his dad.
- Later, when Kun masters riding a two-wheeled bicycle (if barely), the other kids encourage that he'll get the hang of it, laud his determination, and offer they all ride together.
- Kun riding a horse and a motorcycle with his great-grandfather as a means of helping him gain confidence on his bicycle.
- Kun successfully learning to ride his bicycle following said encounter, his father is driven to tears since he never learned to ride one himself as Kun later finds out.
- While reflecting on how Kun developed the determination to ride his bike, Kun's mother points out to her husband that perhaps their son got it from him, as exemplified by how the father's determination to hold Mirai correctly has earned him something precious: Mirai doesn't cry whenever he holds her, now that she's comfortable with him.
- Even though he has a right to be proud, Kun's father humbly and maturely claims that this moment belongs to Kun and his recent accomplishment.
- Kun seeing his great-grandfather's picture and identifying him as his dad. It's an adorable moment that implies how highly Kun looks up to his father. And once he makes the connection that the man in the photo is his great-grandfather, Kun posthumously thanks him for the riding lessons that helped shape his new-found determination.
- Kun rescuing baby Mirai from the Lonely Train as he finally acknowledges he is her brother.
- When Kun and Future Mirai exit the train station through the ceiling, the emotionless conductor briefly smiles up in their direction before calling the next passenger. It's almost as though he is expressing pride at Kun for finally learning his lesson.
- Kun and Future Mirai witnessing the memory of Kun's great-grandfather racing his future wife despite the fact that he's still limping and in pain due to his injured leg.
- The way it actually plays out is worth mentioning. The scene lingers on Kun's great-grandfather, so when his great-grandmother begins running, she immediately disappears. After a few moments of seeing Kun's great-grandfather slowly limping, but pressing on anyway, the great-grandmother comes back into view- stopped. Choosing to let him win.
- In turn, Kun's great-grandfather humbly and sincerely acknowledges his future wife that she's also a very fast runner. Moved by the compliment, she decides to marry him.
- Among these memories, the human representation of puppy!Yukko saying goodbye to his mother before going away to live with Kun's parents. It's a tad poignant (knowing it's a puppy having to depart from its mother), but it's nice to know Yukko got to say a meaningful farewell to his mom before going off to his new life.
- The way it actually plays out is worth mentioning. The scene lingers on Kun's great-grandfather, so when his great-grandmother begins running, she immediately disappears. After a few moments of seeing Kun's great-grandfather slowly limping, but pressing on anyway, the great-grandmother comes back into view- stopped. Choosing to let him win.
- Teen!Kun giving Teen!Mirai a packed lunch and telling her to be more careful about remembering to eat, she offers him a banana to thank him but he refuses.
- Kun offering baby Mirai a banana after witnessing the above exchange and the camaraderie that follows. Mirai even smiles at him - her first smile as a baby in the movie and it was for her big brother.
