Sen grew up as an only child, his family consisting of his father; his mother, too, but only for the first few years of his childhood. His father, a community-renowned Japanese Tea Ceremony master, spent most of his time obsessing over his work. Sen’s mother, an ordinary office woman, grew tired of her husband’s virtual lack of commitment to the marriage and thus left before Sen entered elementary school.

Sen didn’t quite mind not having a mother, however, and spent his days sneaking into his father’s room to watch him work. Sen looked up to his father, and wanted to become just like his role model when he grew up. He started to take an interest in teas and spent half his time bugging his father to teach him about teas and the other half looking at pictures of leaves in various tea books left around the house. And so his childhood was spent. Sen ended up following his dad everywhere and at all times-- at least until school started.

Since Sen grew up mostly inside the house, he didn’t have much contact with other children who spent their time playing outside. However, once he entered elementary school, a whole new world was introduced to him. Sen’s world that had only comprised of his father, had expanded; going to school for the first time showed him that there were actual people his age that he could interact with. He immersed himself in trying to talk to everyone and befriend them.

As Sen was generally good-natured and curious, he was able to get to know many people. He made many acquaintances-- many, but no close friends. In class, Sen kept to himself and was often left out of groups; during breaks he would wander around and chat with others, but ultimately end up sitting alone. His situation made him a bit lonely, but he was too afraid to pipe up and ask to be included, as he believed that his peers wouldn’t welcome someone out of their inner circle.

So his school life continued as normal… until an unexpected project in his later years of elementary school forced him into a group with 5 other people… The group Sen was in made him nervous. Could they get along…? It was a mess at first, but eventually, everyone in the group became tight as brothers.

Sen was extremely happy that he finally had close friends, and was relieved to see their friendship last all throughout middle school and into high school. However, things started getting a bit tense after Hotaru left and came back from visiting his family overseas. Soon afterward, Tamato’s mother passed away, and everyone was shocked and hurt.

Sen graduated soon afterwards, and was sorry to have to leave his friends behind to pursue his dream of educating himself in the art of tea. Unfortunately, he wasn't able to follow his father's career as a Tea Ceremony Master, but since Sen had a good sense of taste and smell, he decided to become a tea sommelier.

For the next 4 years, Sen travelled around and worked odd jobs in cafes and restaurants to gain money and experience to take a tea master course, as well as studying tea by himself. When he was 22 years old, Sen came back to Japan and was surprised that Tamato was planning on opening a cafe in memory of his mother. Sen was worried about his friend’s state when Ai had died but he now saw that Tamato was trying to follow up on his mother’s dream. Grateful that he could help, Sen decided to join.