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From early on, it becomes obvious that Makoto has a mischievous personality, which leads to her performing various pranks. These are done exclusively on Yuichi because of her strong dislike for him, something she constantly reaffirms. Her persistent attempts at pranks on Yuichi vary in severity, such as simply dropping food on him or once even throwing lit firecrackers in his room. However, he manages to turn each prank back on her, which makes her all the more determined to successfully prank him. As time passes and Makoto begins to feel more as a member of the Minase family rather than a stranger, she honestly grows to like Yuichi, effectively looking beyond her latent distaste for him. Soon after her attitude changes, she starts weakening and eventually becomes incapable of communication because her wish to be at Yuichi's side would only last for a short period of time. Makoto falls in love with Yuichi and says she wants to be married to him and stay with him forever. At the end of her story, after she and Yuichi have been "married", she disappears in front of Yuichi, and is presumed to have died. In the last episode of the series, a fox appears behind the stump of the tree where Yuichi and Ayu played at. It is not confirmed that this is Makoto, presumably the fox is just a reminder of her.
Makoto is in fact not a human being but instead a fox that Yuichi found ten years prior to the beginning of the Kanon story. Yuichi first found Makoto, then a young fox, injured on Monomi Hill and he took the fox back and kept it in his room for the rest of the summer. One day, Yuichi tells the fox about an older girl that he had a crush on named Makoto Sawatari, which is where Makoto's name is derived from when the Kanon story is just beginning. At the end of summer break, Yuichi takes the fox back to the hill, and he runs away soon after releasing her, leading her to be angry with Yuichi. With her desire to see Yuichi being so strong, her wish was granted at the cost of her memories and later her life. The two later reunite after the fox transforms into Makoto near the start of Kanon.