Yudai is serious and gentle yet shy and timid, especially when expressing his true feelings to Chizuru, the girl he loves. Past romantic failures, including an incident where he fainted in front of a previous girlfriend after climbing stairs to avoid her dog, fuel his lack of confidence and tendency to avoid confrontations.

He plans to gift Chizuru a rabbit for their first Christmas together to convey his affection. An accidental swap results in him giving her a mini-donkey instead, triggering misunderstandings. His initial reaction involves making incorrect assumptions and failing to take responsibility, highlighting his struggle with emotional vulnerability.

Facing potential separation as Chizuru considers ending the relationship due to mutual insecurities, Yudai reaches a turning point. He overcomes his fears in a pivotal moment involving Tokyo Tower, demonstrating personal growth by actively pursuing reconciliation. This culminates in his ability to openly confess his feelings to Chizuru, resolving their misunderstandings.

The mini-donkey inadvertently facilitates this journey toward emotional honesty, acting as a catalyst for confronting his insecurities. His background shows a pattern of retreat from romantic challenges, but through the shared experience with Chizuru, he evolves into someone capable of expressing love directly despite past setbacks.