Highschool of the Dead: Drifters of the Dead

In both productions participates a group of students lost on a deserted island, besides having fanservice moments, being those of HOTD: Drifters of the Dead more intense. 

Two OVAs which leave aside the action and gore of the main anime and put the characters on a tropical island to focus entirely on the ecchi and comedic elements, to a point in which it's ludicrous. Ecchi fans will have a field day with these two OVAs. 

The story of both is lovely and is funny at times. School-live wants to bring hope and happiness to Yuki to protect her whereas in HOTD: DOTD the whole characters all have their own quirks that make them who they are. Both of these have similar areas as well such as survival, zombie, friendship, and family. Both stories, all the characters have to “grow” in their own ways to overcome the apocalypse. 

Group with majority of girls gets on an island. Sexual situations intensifies. While Highschool of the Dead: Drifters of the Dead is heavy ecchi, Naoko no Tropic Angel: Hyouryuu is hentai.  

HotD OVA basically ripped off the Akane-iro OVA. They're essentially the same. Neither of them has any story and are basically just ecchi all the way trough. 

Both are on a beach, and have similar moments, but HOTD is a lot more intense and graphic than To aru :Railgun OVA. both are very ecchi 

To me both "High School of the Dead: Drifters of the Dead" and "Higurashi No Naku Koro Ni Kira" are a bunch of what if's to the whole story far from their original intention. Higurashi No Naku Koro Ni Kira, however is a type of OVA w/ multiple short stories, while HOTD Drifters of the Dead only focuses on one story. One similarity between the two is the use of fan service, however HOTD Drifters of the Dead does obviously contain a much more mature type of this fan service. 

Equally full of fan service despite salvageable content in the parent series.