Hajime Shinshiro

Rin's maternal grandfather. He is the person who inspired Rin to start solo camping when she was in middle school. He has a distinguished appearance with a white Castro beard on his chin and cheeks. His home is believed to be in Aichi Prefecture.

He gave Rin a set of camping gear he used previously and now spends his time traveling year-round on his motorcycle. In the original manga, he is mentioned in a phone conversation with Saki in Chapter 11 (Episode 7 of the anime) and is referenced in conversations between Rin and Nadeshiko. He makes his first appearance in Chapter 28 of the manga, where he picks up Rin, who is stranded due to snow-covered roads, and drives her back from Shizuoka. The day before Rin's camping trip to Izu, he delivers a motorcycle screen from his home, notices that the cable connecting the bike to the smartphone lacks a relay, and goes to buy one. He then helps install the parts on Rin's scooter with Wataru and accompanies Rin partway on her trip the next morning. Although he claimed the motorcycle screen was something he had at home, he actually bought it specifically for Rin, showing his deep affection for her.

In the TV anime, his appearance is moved up, and an original episode in Episode 6 of Season 1 shows him meeting Chiaki while scouting a campsite (though it is not revealed that he is Rin's grandfather at this point). His appearance is also depicted earlier in the anime during the phone conversation with Saki mentioned above.

In the TV anime, Akio Otsuka, who also serves as the narrator explaining camping gear and other details, voices him. In the live-action drama's second season, his face is partially shown in a car's rearview mirror, and his back and arms are visible, with Otsuka providing the voice.