Based on the erotic game by Atelier Kaguya Bare & Bunny. 
 
The protagonist is a famous soccer player, but due to a leg injury from a game, he must now rest until it heals. When he returns home, he is warmly greeted by his 4 older sisters whom he hasn't seen for a long time. 
 
However, because his clubmates have play a prank on him and fill his bag with ero manga, their relationships immediately plummet after they find out about it. 
 
While trying to explain the situation to no avail, one of them suggests that they themselves should help him escape the 2D world and be interested in healthy adult women. Little does he know, all of his sisters love him more than a brother. 
 
And so, this is the beginning of a ridiculous erotic life between our protagonist and his 4 tempting older sisters. 
 
(Source: Official Site) 
 
Note: A director's cut edition was released 2017/09/29 with additional scenes added.

Baku Ane: Otouto Shibocchau zo! THE ANIMATION