"Nanase Mitsuki is a prominent character in the Japanese manga ""Falling Blue"". Mitsuki is a seventeen-year-old high school student and a member of the school's swim team. She has wavy, dark brown hair that she usually ties back into a ponytail and large, expressive brown eyes. Mitsuki stands at an average height and has a lean yet athletic build.

Mitsuki is known for her competitive spirit and fierce determination. She is a talented swimmer and often puts in long hours of training to perfect her technique. As a result, she has won numerous awards and medals at local and national swim meets. Mitsuki takes pride in her abilities and is often seen helping her teammates and pushing them to be their best.

Despite her success in the pool, Mitsuki struggles with personal issues that weigh heavily on her mind. She tends to keep her emotions bottled up and rarely expresses her true feelings, except with a select few close friends. Mitsuki also has a tendency towards perfectionism, which can cause her stress and anxiety.

Mitsuki's personality and struggles are revealed further when she starts a romantic relationship with a classmate named Tomoya. The two bond over their shared love of swimming and eventually become a couple. However, Mitsuki finds it difficult to open up to Tomoya about her personal issues and fears that he will not understand her. Their relationship is tested when Mitsuki's anxiety becomes overwhelming, leading to a breakdown that reveals her deepest fears.

Throughout ""Falling Blue"", Mitsuki's character demonstrates that even the strongest people have vulnerabilities and that it is important to have a support system of friends and loved ones. Her determination and passion for swimming serve as an inspiration for others, while her struggles with anxiety and perfectionism make her a relatable and complex character."