My Friend's Little Sister Has It in for Me! Volume 8 (Light Novel): Volume 8

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!