Boku to Kimi to de Niji ni Naru

Rui has a strong dislike for the words "waste" and "fuzzy" due to her fondness for the word "wisdom." When a man named Shou enters her life, she begins to undergo unexpected changes. The story unfolds as this very serious and reserved girl interacts with Shou, a more laid-back and carefree individual, leading to a series of events described as a "rainbow school daze."