Rie Sekiguchi (関口 梨恵) works as an office lady alongside Rena Yukuhashi and Ryohei Hachiya. She has auburn hair and red eyes, creating a visual contrast to Rena's reserved demeanor. Her personality is bright, stylish, lively, and friendly, often displaying an open and sociable attitude at work. Unlike Rena, Rie confidently expresses her charms and maintains a fashionable presence among colleagues. Her behavior and appearance unintentionally fuel relationship tensions between Rena and Hachiya when Hachiya falsely presents Rie as his romantic preference to conceal his affair with Rena, causing Rena significant distress. During a company beach trip, Rie actively searches for Hachiya and interrupts him and Rena engaged in intimacy inside a car. Unaware of their activities, she initiates an interaction where Rena continues the encounter while Hachiya responds to Rie through the car window.