Haikei, Tengoku no Neesan, Yuusha ni Natta Mei ga Ero Sugite ーー Ojisan, Hogosha Toka Sorosoro Muri Desu+拝啓、天国の姉さん、勇者になった姪がエロすぎて──叔父さん、保護者とかそろそろ無理です＋(ぷらす); Haikei, Tengoku no Neesan, Yuusha ni Natta Mei ga Ero Sugite Ojisan, Hogosha Toka Sorosoro Muri Desu (Purasu); Dear Big Sister in Heaven, My Niece Who Became the Hero Is Too Erotic. Signed, Her Uncle. Being Something like Her Guardian Will Soon Be Impossible for Me+; My Niece Who Became Brave is Tooooo Erotic.

Angel, a former top-tier mercenary, was forced to retire due to an injury. Left by his fiance, he now spends his days drowning in alcohola middle-aged adventurer (and a virgin). One day, his niece Liz, whom he once taught swordsmanship, suddenly barges into his life! Angel is bewildered by how she has grown into an astonishingly beautiful girl, but Liz pays no heed to his hesitation and boldly declares that she will become his wife?! A heart-pounding fantasy adventure, in more ways than one, featuring a beautiful young heroine and her middle-aged uncle!