Kousui Kanda is a novelist traveling with his son, Akane Kanda, following the death of his wife. He possesses long black hair and a short, unshaved beard. He embarked on this journey specifically to help Akane cope with depression and grief after losing his mother, demonstrating concern for his son's emotional well-being.

During their travels, Akane developed a fever, prompting Kousui to seek shelter by the roadside. Oriko Seki discovered them and brought them to Hananoyu Inn after other local accommodations were full. After Akane's fever improved, Kousui expressed gratitude to the inn staff. When Matsuki Akino, representing the larger Shuukou Lodge, attempted to persuade him to transfer there for more luxurious accommodations, Kousui chose to remain at Hananoyu after hearing Oriko express her commitment to providing genuine service. This decision reflected his prioritization of supportive care over material comfort for Akane.

While staying at the inn, Akane requested cake, which the inn did not have. Oriko created a "hot bath" pudding resembling hot spring water as an alternative. Kousui and Akane deeply appreciated this gesture. Kousui later authored a magazine review praising the inn and specifically highlighting Oriko's efforts. This review significantly boosted the inn's reputation and attracted new guests.

Information regarding Kousui Kanda's involvement in other official media such as OVAs, spin-offs, or expanded storylines beyond this initial appearance and his departure from the inn is not available. His narrative centers on this period focused on supporting his grieving son and the consequential stay at Hananoyu Inn. The name Kousui translates to "happiness, good luck" (幸) and "water" (水), while his surname Kanda means "god, deity" (神) and "field, rice paddy" (田). No further character development or background details beyond this storyline are documented.