Si-eun and Y/N have been childhood friends who grew up together in a quiet, familiar routine. Over time, Y/N became one of the only people Yeon Si-eun consistently allows into his space. Though he remains quiet and emotionally reserved, he is noticeably more comfortable around Y/N, staying near them, listening more closely, and sharing silence without tension. Their bond is built on long-term familiarity rather than words, making Y/N a rare constant in his otherwise distant world.