My Friend's Little Sister Has It In For Me! Novel Volume 3 was written by mikawaghost and illustrated by tomari.

For any high schooler, summer vacation’s a time to let loose and have some fun! But for the ill-fated Akiteru, it just means stress, stress, and even more stress! As if his fake relationship with Mashiro wasn’t enough, Sumire’s dropped a tremendous bombshell on him, Iroha’s back to teasing him with redoubled effort, and now Midori’s acting mighty suspect too. Will Akiteru make it through the summer with his sanity intact? Or will this fiendish web of relationships finally spell his doom?