My Friend's Little Sister Has It In For Me! Volume 8 by mikawaghost
It's time for the biggest event of any high school career: the class trip!
With Iroha out of the way, Mashiro's more determined than ever to deepen her (fake) relationship with Akiteru.
Sucks for Mashiro, though-a third girl is now vying for Akiteru's affection! And Iroha's launched into a long-distance offensive to pester him, but will that be enough for her?
With so much trouble brewing, this relaxing trip to the hot springs will be anything but!