"Yui Yamaguchi, the main character of ""It Starts With A Mountain,"" is a 16-year-old high school student who lives in a small town in Japan. She is portrayed as a shy and reserved girl who doesn't have many friends.

Yui has long brown hair that she often wears in a ponytail, and she has dark brown eyes. She is quite short, standing at only 5'2"" tall. Yui is often seen wearing her school uniform, which consists of a white blouse, a navy blue skirt, and black knee-high socks.

Despite being quiet and introverted, Yui has a fierce determination that drives her actions in the story. She is determined to save her town from the negative impact that a proposed ski resort would have on the local environment. This puts her in direct conflict with the developers of the resort, who are more concerned with making money than preserving the natural beauty of the area.

Throughout the story, Yui learns to stand up for herself and speak her mind despite the obstacles she faces. She also forms new friendships and deepens her relationships with the people around her, including her family and fellow activists.

Yui's love for the mountains and the natural world is a central theme of the story. She is an avid hiker and spends much of her free time exploring the nearby mountains and forests. Her deep connection to the land gives her the strength and motivation to fight against the development of the ski resort.

Despite facing challenges and setbacks, Yui remains determined to stop the resort from being built. Her courage and perseverance inspire those around her, and she ultimately succeeds in her efforts to protect her home and the natural world she loves.

In conclusion, Yui Yamaguchi is a complex and inspiring character in ""It Starts With A Mountain."" Her quiet strength, love for nature, and determination to do the right thing make her a compelling protagonist who readers will root for throughout the story."