Hakari and Karane are putting themselves through a series of trials to see who is more worthy to have sex with Rentarou first. In this trial, they walk along the knotted rope and see who can last the longest and get the furthest. Hahari helped with the set-up and "accessories".

(Commissioner/Source):
https://www.pixiv.net/en/artworks/124734086

(Artist):
https://www.pixiv.net/en/users/31634459
https://x.com/nerokun16