Yuuta Segawa starts his first year in college. He meets second year Raika Oda under unusual circumstances thanks to Sako and Nimura of the Street Observation Research Society. Meanwhile, Yuuta bumped into Raika again had a uneasy conservation with her and as she left he starts to have a crush on her. After joining the Street Observation Research Society for 3 months, he meets up with his sister and misinterpreted him with seeing Raika. His sister asked him to visit Sunday to see her kids. However, it turned out into a babysitting task for the kids while they are out for awhile which his sister neglected to say. His conversation with his nieces were quite awkward.

Yuuta awakens to find Sora hugging him. She starts screaming when she finally awakens. Yuuta leaves the three girls in his apartment with an instruction never to leave home and never answering the door. Yuuta was later ambushed by Raika and the rest of the Sightseeing Club for him not visiting them in awhile. Meanwhile, the girls had to do something, given the rather huge bill for their breakfast. They tidy the room, head to the laundry shop, and shop for vegetables for dinner, though Hina starts writing on the wall with permanent pens and making dinner being a disaster. Though Yuuta, coming home late, gets upset with what happened, his being upset is replaced by happiness, because he understands the thought of all of it counts.

Yuuta takes Sora, Miu, and Hina out of their house before his relatives would come to take them. While eating lunch at a karaoke box, Kouichi attends to the three, as one of Yuuta's relatives calls, asking him to bring the girls back. Only then that he realizes the full scope of the challenge he has gotten into. Despite this, Yuuta carries on, and brings the three girls to his apartment. Meanwhile, Sora and Miu is trying their best to adjust to living in Yuuta's apartment while getting a grip on things and accept them as they are, amidst Hina's asking for her mother and father. Sora, meanwhile, is glad that she and her sisters are not going to be separated.

The main character, a college freshman just starting a new life in the School of Literature at Tama University. His parents passed away when he was young. As such, he was raised by his sister, Yuri. He was angry with his sister's decision to marry a man who has two daughters from previous marriages. When Yuri and her husband went missing, their three daughters had no one to turn to. Yūta makes a decision to take them in and becomes their guardian. He is surprisingly reliable. Even the youngest daughter of the three, Hina, quickly got close to him. He has feelings for Raika.