|Rōmaji||Kindan no Ooru Haado!|
|Air Date||March 18, 2015|
|Opening||Dried Up Youthful Fame|
|← A Distant Tremble!||Buildup of Early Spring! →|
Forbidden All Hard! (禁断のオールハード！ Kindan no Ooru Haado!) is an Original Video Animation (OVA) included as extra material when Free!-Eternal Summer- was released on March 18, 2015.
The Iwatobi swim club members attend the Samezuka annual cultural festival. Upon arriving, Haruka Nanase bumps into a pretty young maid who turns out to be Aiichiro Nitori who explains to the club that the Samezuka swim club traditionally runs the 'Maid Café from Hell'. When greeted at the cafe, the club runs into Momotaro Mikoshiba, Rin Matsuoka shortly shows up informing Haru and the others that he, Momo, Nitori and Sosuke Yamazaki are going to go on break so they can wander the festival with them.
Later, the group eventually comes across a stall advertising a water fight competition, which catches Haru's attention for multiple reasons (some of the kanji used on the sign could also be read as mackerel). The group splits into two teams: Red and Blue. Team Red consists of Rin, Makoto Tachibana, Nitori & Rei Ryugazaki, while Team Blue contains Haru, Sosuke, Nagisa Hazuki & Momo.
The ensuing water fight takes many dramatic turns with several shock confrontations, traps, and a few unfortunate encounters for Kisumi Shigino. Ultimately, the fight boils down to a showdown at sunset between Rin and Haru which results in a win for Team Red thanks to Haru's immense love of water. Following the fight, the group gathers around the bonfires at the festivals conclusion where they all dry off and have an animated and long discussion, including the prospect of the Samezuka team attending the Iwatobi cultural festival in the future.
List of characters in order of appearance: