The events of Secret Recipe 2 have direct repercussions in the events of this doujin. There are two parts:
In the first part, Hisako finds the photos that Alice sent Erina at the beginning of Secret Recipe 2 and decides she can’t tolerate Erina have sex with Yukihira. Instead, she’ll take care of his sex drive. It just so happens that she get a bit to much into it...
In the second part, Alice is frustrated for not being able to defeat (?) Erina in the sex competition they had in Secret Recipe 2 and decides to enlist Ryou to practice sex. He’s not into it at first, but after she forces him to put on his bandana, she gets more than she bargained for...
Working as a Secretary Ship, Kaga notices that the Admiral was redirecting the naval base resource into funding his sexual escapades with various shipgirs. In the ensuing argument, the Admiral jokingly remarks that she should just relieve his sexual tensions in place of other girls.
Kaga doesn’t take it as a joke.
The poor admiral has yet to realize that he has just stepped on a land mine and delivered himself straight into the hands of an insatiable sex fiend hiding under Kaga’s cool demeanor.
Turns out Alice stumbled upon Souma and Erina having sex (in the first volume) and is now using photos to blackmail Erina into… wearing a bunny costume together with her???
Once both of them are in the bunny outfits, their competitive spirit kick in and they start competing in… pleasuring Yukihira???
What were expecting? Cooking?