It is not easy to find anime soundtrack which features a male and a female performing duet songs.
Although there are limited options of this type of song, it is usually worth listening too.
Most of them are beautifully arranged.
Here are my findings on list of anime duet songs :
1. Yume no Tsubasa (Tsubasa Chronicle) ~ Miyu Irino & Yui Makino
– Sang by both seiyuus of Shaoran and Sakura. This song feels romantic.
2. Katakoto no Koi (Chobits) ~ Tomokazu Sugita & Rie Tanaka
– Sang by both seiyuus of Hideki and Chii. Catchy Songs.
3. Gekkou Symphonia (Aquarian EVOL) ~ AKINO & AIKI
– Sang by siblings Akino and Aiki Kawamitsu. Theme song from recent anime Aquarion EVOL. This song has an angelic feeling.
4. Little Goodbye (Zegapain) ~ ROCKY CHACK
– Not exactly a duet song, but still nice to listen
5. “And Forever…”(Big O) – Robbie Danzie with Naoki Takao
– Pretty romantic English songs from a classic anime.
6. “Moment” (Gundam Seed) – Vivian Hsu and Kazuma Endō
– Rare soundtrack by Taiwanese actress Vivian Hsu.
7. “Ai no Zuellni feat Leerin Marfes” (Chrome Shelled Regios)
8. “Ai no Zuellni feat Mayshen Torinden” (Chrome Shelled Regios)
– There are two versions of this duet, between the main singer and one of the female seiyuus.
9. “Yasashii Uso feat Feli Ross” (Chrome Shelled Regios)
10. “Yasashii Uso feat Nina Antalk” (Chrome Shelled Regios)
11. “Yasashii Uso feat Leerin Marfes” (Chrome Shelled Regios)
– There are three versions of this duet, between the main singer and one of the female seiyuus.
12. “Moon on the Water (Maho ft Koyuki)” (BECK)
– Very classic duet song from memorable music themed anime. Hey, and it’s in English!
13. “Stand Up Year” (Dog Days 2)
– From the 2nd season of anime Dog Days. At least I know the female voice is Yui Horie’s.
14. “Runner” (Macross)
– Wow, a super classic jpop
15. “Runner” (Macross)
– Wow, a super classic japanese song
16. “Honey Honey” (xxxHOLiC)
– Very unique duet song, with the male rapping and female voice acts as background sound or punchline.
17. “Totsugeki Love Heart (Duet Version)” (Macross 7)
– This is one fiery song. I believe the duet version was released long after the anime broadcasted.
For other type of unique songs, you might also want to check Anime A Capella Songs.