Boku no Futatsu no Tsubasa

Boku No Futatsu No Tsubasa is a manga by Yui Toshiki.

It opens with schoolgirl Hiromi being excited that her cousin Mako is coming to stay with her and her mother. Hiromi remembers playing with Mako when they were little, and is hoping "he" has grown into a handsome young man. However, when Makoto shows up as a very buxom young woman, it starts of a chain of misunderstandings, secrets and cover-ups.

This is an Ecchi manga and features adult situations, explicit sex scenes, and nudity. Some of this is played up as fanservice, but there is a lot of sex tied into the plot as well.

The manga includes examples of:

A Date With Rosie Palms: Mako-chan, which often leads to...
- Caught With Your Pants Down: As Hiromi frequently walks in on her.
Action Girl: Mako can kick much butt when the need arises.
All Men Are Perverts: Averted with Hisamatsu, but played straight with his friend Keigo.
Barbie Doll Anatomy: Runs on the standard Rule of Ecchi -- nipples are fair game, genitals aren't drawn.
Berserk Button: Don't call Mako-chan a monster.
Bi the Way: Both Makoto and the resident Casanova, though the former eventually settles on women, and the latter is basically not all that choosy to begin with.
Bizarre Alien Biology: Mako-chan and her "father".
Boldly Coming: Inverted. Here, it is the aliens who initiate "first contact", and not because Mars Needs Women.
Book Ends: It starts and ends with Hiromi opening the door, expecting somebody else, and being surprised when Mako arrives. The panel layouts and character movements are the exact same as well.
Buxom Is Better: Most of the guys, and a few of the girls are impressed with Mako-chan's ample chest, which is an F-cup.
Everybody Wants the Hermaphrodite: Mako herself seems to prefer girls: she has the thought that the only people who really accepted her as she was were girls. (The two guys she dates don't exactly leave her a great impression of men.)
Gainax Ending: More of a highly rushed ending, but it does resolve the plot in an almost lightning speed manner that is a little confusing to follow.
- The majority of the series is spent being a kind of Slice of Life Romantic Comedy revolving around how to keep the fact that Mako is a hermaphrodite a secret with a mysterious force in the background. The last few chapters kick in with it being revealed that Mako is actually an alien, people want her to hold for ransom so they can get alien technology from her father, she then goes back to her father's homeworld... and comes back to Earth again in the last few pages.
Glowing Eyes of Doom: When Makoto's alien powers kick in.
Hermaphrodite: Mako
Hot Amazon: Keigo suddenly becomes interested in Mako after she beats up a group of muggers trying to steal her mobile telephone.
Human Mom Nonhuman Dad: Mako and her parents.
If Its You Its Okay: Kanna's reaction to being deflowered by Mako and also straight with Keigo. Averted with Hisamatsu who says they're okay with it but when it came down to it... it didn't go as planned.
Interspecies Romance: Makoto's parents. And to some extent, every romance involving their daughter is that.
Lethal Chef: Eating all of Makoto's bentou is a very bad idea.
Luke I Am Your Father: Hiromi's adoptive mother is actually Mako's mother.
Making Love in All The Wrong Places: Both Makoto and Hiromi use the nurse's office (not with each other), and Mako also makes use of various other locations around the school with Kanna.
Older Than They Look: Ayame looks like she's about twelve.
Playing Doctor: Mako-chan and Hiromi as kids, leading to some amusing misconceptions.
Schoolgirl Lesbians: Kanna, Tamami and Hiromi, sort of.
Sister Sister Incest: Mako and Hiromi at the very end, although they are Not Blood Siblings. The way it is brought is a bit... sudden though.
Teacher Student Romance: Mako catches Keigo cheating on Hiromi with one of the school's teachers.
Transsexual: Tomoki, who describes herself as "a girl trapped in a boy's body".
Yuri Genre: A good part, if not most of the romances are between girls. Although Mako is a hermaphrodite her female side is clearly prominent (except during sex).