Ep. 4: Narue discovers her older sister Kanaka, who mistakes her for Tadashi's wife before learning the truth.

4

Narue learns that her older sister, Kanaka Nanase, is visiting with her caretaker, Bathyscaphe. Kanaka mistakes Narue for Tadashi's wife and runs away in anger. After realizing Narue is her sister dating Kazuto, Bathyscaphe beams Kazuto aboard. Kanaka discovers Narue is technically older due to the Urashima effect. Bathyscaphe lands and reconfigures into a house. Narue shares memories of her late mother and visits Kanaka, who is upset about Tadashi's changes. Kanaka accidentally shocks Narue with a stun gun, causing a high fever. Believing she is unloved, Kanaka is reassured by Kazuto that Narue eagerly awaited their meeting. The group waits all night until Narue wakes up the next day, bringing Kanaka happiness.