We have all done some odd jobs to make a little extra money, and voice actors are no exception. Some popular voices even got a start voicing hentai and eroge. Hey, it's a good way to gain experience. Just ask these voice actors.
Known as: Kazumi Asakura (Mahou Sensei Negima!)
Also voiced: Yuuki Miyagishi (Discipline)
Known as: Irina Jelavić (Assassination Classroom) / Minako Aino (Sailor Moon Crystal) / Hinagiku Katsura (Hayate the Combat Butler) / Akeno Himejima (High School DxD)
Also voiced: Hiiragi Kaede (Duel Savior) / Arimiya Chisato (Jokei Kazoku ~Inbou~) / Kazama Touko (Muv-Luv Alternative) / Kisaragi Mifuyu (Tayutama -Kiss on My Deity-)
Known as: Mikuru Asahina (The Melancholy of Haruhi Suzumiya) / Anya Alstreim (Code Geass)
Also voiced: Eimeiyo (Ore no Tsure wa Hito de nashi) / Yukie Mayuzumi (Maji de Watashi ni Koi Shinasai!)
Known as: Kurisu Makise (Steins;Gate) / Chihaya Kisaragi (The iDOLM@STER)
Also voiced: Rena F. Avery (Walkure Romanze: Shōjo Kishi Monogatari) / Chelsea Arcot (Shukufuku no Campanella)
Known as: Nami (One Piece)
Also voiced: Lydia (Dragon Rider) / Momomi Momoi (Mezzo Forte)
Known as: Pikachu (Pokémon) / Tony Tony Chopper (One Piece)
Also voiced: Kana (Cool Devices) / Karisu (Dragon Rider)
Known as: Sanae Furukawa (Clannad) / Lust (Fullmetal Alchemist: Brotherhood) / Bellandy (Oh My Goddess!)
Also voiced: Misako Narusawa (Dōkyūsei 2) / Ruko Tatase (Ogenki Clinic Adventures)
Known as: Ougi Oshino (Owarimonogatari) / Mami Tomoe (Madoka Magica)
Also voiced: Michiru Matsushima (The Fruit of Grisaia)
Known as: Caldina (Magic Knight Rayearth) / Mimori Kiryu (S.CRY.ed)
Also voiced: Rena Asaoka (Lingeries)
Known as: Yua Kusunoki (Chaos;Head) / Kanako Sanjo (Terra Formars) / Azusa Miura (The iDOLM@STER)
Also voiced: Kumiko Mikami (Hitozuma Ryoujoku Sankanbi) / Mitsuki Hayase (Muv-Luv) / Nanami Kanroji (School Days)
Known as: Rider (Fate/stay Night) / Leon (Akame ga Kill!) / Sakaki (Azumanga Daioh)
Also voiced: Aemiria (Tears to Tiara II: Haō no Matsuei) / Misae Munakata (Muv-Luv) / Momoyo Kawakami (Maji de Watashi ni Koi Shinasai!) / Misuzu Kusakabe (11Eyes)
Known as: Yuri Nakamura (Angel Beats!) / Lisanna Strauss (Fairy Tail)
Also voiced: Saori Asou (15 Bishoujo Hyouryuuki) / Momoko Hanamaru (Ane to Boin) / Haruka Kagami (Helter Skelter: Hakudaku no Mura) / Nazo no Ninja (Rance 01) and many more.
I think Harumi Sakurai voices mainstream anime for fun. Look at that beautiful resume.
Who are your favorite voice actors that have done hentai and eroge?
I've been hooked on sci-fi, space, and anime ever since watching Trigun, Outlaw Star, and Cowboy Bebop. I love exploring shows and subjects that have been passed over, especially shows based in unusual settings, so expect recommendations that are a bit further from the mainstream. I take about 4 major trips a year and love to visit the local fan conventions when I can.