Chiyo's summer house is where Chiyo Mihama's family spend their summer, and to which her friends and even teachers are often invited. It's large and close to the sea, as well as a summer festival.
Year 1During the summer vacation of the girls' first year at high school, Chiyo invites some of her new friends to her house. Osaka suggests they all go and have fun somewhere, and Chiyo says they can come to her summer house if they want, which impresses the others since her family is not only rich enough to afford living in a mansion, but also to own a summer home of their own. Osaka, Tomo, Yomi, Sakaki, and also Yukari and Nyamo are the guests, since the teachers said they had to come when Chiyo called them to ask permission. Unfortunately, the experience is somewhat ruined for Chiyo and Osaka who had to ride with Yukari in her car. Tomo is determined to succeed with splitting a watermelon using only her bare hands. Yukari also uses fireworks when the night comes. Osaka also tells a ghost story about all the girls getting murdered with herself turning out to be the culprit in the end.
Year 2The second time around, newcomer Kagura comes with the others and Tomo appears to be proud about having seen Chiyo's mansion and summer house before she did. When they get to the house, Tomo snatches the key from Chiyo and throws it in the grass just for fun, so that everyone has to look for it, and finally they find it. Tomo also bugs the others when they try to sleep and is revealed to be the first to fall asleep and wake up in the morning. The girls also visit a nearby summer festival, and Chiyo and Sakaki are the only ones who know how to tie a yukata. Nyamo gets very drunk because she drank the beer and sake brought by Tomo and Yukari. The girls convince her to share her sex life experiences, which she willingly does, making them thankful but uncomfortable. Chiyo on the other hand doesn't understand anything, and in the morning, Nyamo is hung over, remembering nothing about what she said the night before.
Year 3For the girls' third trip, Kaorin joins them and is, much like Chiyo, scarred from riding in the Yukarimobile. This time, everybody has to study for the college entrance exams. Kaorin tries to take pictures of Sakaki, though Tomo gets in the way. Chiyo and Sakaki also do radio exercises. A half-asleep Osaka tries to wake up Yukari with a frying pan, though she takes a knife from the kitchen instead by accident. This scares Yukari as Osaka walks into her bedroom holding the knife, unaware of her mistake, and saying that she might try it again.
Supplementary LessonsAzumanga Daioh: Supplementary Lessons contains additional information on what the girls did during this trip. Tomo and Osaka go to catch cicadas, and it is revealed that Yomi hates them. Tomo is mean enough to place one on Yomi's back, and Kaorin tries to catch it using a net. Osaka starts giving stamps to people who are nice to her, and Nyamo, Kagura and Sakaki play volleyball. When she notices Kaorin's admiration of Sakaki, Osaka asks her if she is gay, which makes Kaorin very nervously try to deny it. Yukari says she wants Nyamo to come to work by horse, pulling a carriage that she could ride in, but Nyamo turns her down. They also look at the stars, and Kaorin informs Sakaki about constellations, information she gained from being a member of the Astronomy Club, though she does not do the same for Tomo.
- It is unknown where the house is situated.
- Chiyo's parents are never seen around the house, for unspecified reasons, and neither is Tadakichi-san.