"Yuika Koga is a main character in the manga ""The World for Your Smile."" She is a high school student and a member of the school's photography club. Her name appears multiple times throughout the series as she is an important member of the cast.

Yuika is a very kind and caring person who is always looking out for her friends. She is a talented photographer and takes stunning photos that capture the beauty of the world. Her love for photography is evident in the way she talks about it and the way she handles her camera.

Despite her kind and caring nature, Yuika can also be somewhat shy and introverted. She often struggles to open up to others and make friends. However, as the series progresses, we see her become more confident and willing to put herself out there.

Yuika is also something of a romantic at heart. She has a crush on one of her fellow photography club members, and we see her struggle to express her feelings throughout the series. Her feelings for him are a constant source of both joy and pain for her.

Overall, Yuika Koga is a well-rounded and well-developed character in ""The World for Your Smile."" Her love for photography, kind nature, and romantic struggles make her an endearing and relatable character."