Anime & Manga Character Archetypes
Taken from forum posts of 3 & 5 February 2008 and revised.
Jatz:
Older Woman? I don't really know how you define "older".
See The Erotic Anime Movie Guide 1 chapter 9, "Sex with the Girl Next Door: The Roots of the Anime Erotic", especially pages 101-103. There are six archetypes: the Girl Next Door ("bland, nice, clumsy"), the Tomboy ("tough boyish, feisty"), the Maiden ("sweet, girlish, meek"-a yamato nadeshiko, though the rich, arrogant ojō-sama 2 (お嬢様) is also a Maiden-and, in non-erotic anime, unattainable), the Older Woman ("mature, sophisticated, intelligent"), the Alien ("sexual, disposable, idiot"-someone "not from around here"), and the Child ("immature, unsophisticated, idiot savant"; sometimes feral, sometimes not).
The Older Woman archetype is basically any mature woman-someone older and more mature than the target audience (usually with a bust to match); a character in her twenties is often the Older Woman. E.g., (adult) older sisters, mothers, teachers, bosses... In erotica, the Older Woman category is particularly geared toward the jukujo (熟女 "mature lady" (lit. "ripe woman")), stereotypically a bored and neglected housewife, often in a second marriage, who may or may not yet have had her Inner Slut™ awakened (since the Japanese believe a woman reaches her sexual maturity in her thirties and forties, though in this case the stated age of the character is still not important).
Taking Sailor Moon for example, Usagi/Sailor Moon is the Girl Next Door, Makoto/Sailor Jupiter is the Tomboy, Ami/Sailor Mercury and Rei/Sailor Mars are the Maidens, Setsuna/Sailor Pluto is an Older Woman, Minako/Sailor Venus can fill the Alien role (due to her time in England), and Chibiusa/Sailor Chibi Moon is the Child.
Regarding subtypes, Ai Yori Aoshi 's Aoi Sakuraba and Ranma ½ 's Kasumi Tendou are quiet Maidens; contrast them with the arrogant ojō-sama-type Maiden Sumire Kanzaki from Sakura Wars. Blonde, brash, and buxom Tina Foster of Ai Yori Aoshi is (on the surface) the stereotypical Alien. Tanya Natdhipytadd of Battle Athletes / Battle Athletes Victory is an example of a feral Child.
Anyway, to answer Jatz's original question, Megumi Asahina of Virgin Touch does count as an Older Woman.
The Erotic Anime Movie Guide also posits six male archetypes in Chapter 4 "Pretty Boys in Pain: Shounen Ai Anime" (pages 32-41). Examples from Bleach, which is what I was watching at the time I originally wrote this:
Big Brother (protective, responsible, noble "sempai"): Yasutora "Chad" Sado, Uryū Ishida
Boy Next Door (average, shy, bland): most eroanime protagonists, so that the viewer can identify with them.
Local Hero (tough, valiant, flashy): Ichigo Kurosaki
The Older Man (mature, sophisticated, intelligent): Kisuke Urahara, Tessai Tsukabishi
Kid Brother (immature, unsophisticated, idiot savant): Jinta Hanakari, Yūichi Shibata (the cursed "parakeet" (actually a cockatiel) featured in episode 4)
The Stranger (forbidding, dangerous, enticing): Kisuke Urahara (also)
More examples (from eroanime): The women in Office Lingerie (AKA Lingeries) are technically all Older Women, but they fill the following archetypes:
Girl Next Door: Mayumi Fujiyama (the clumsy, energetic girl of Planning Section 2 who invents the "seamless" lingerie)
Maiden: Chisa Sakurai (the very busty meganekko in R&D)
Older Woman: Reina Asaoka (the cool brunette in Marketing)
Alien: Alice Nonoyama (the blonde (Japanese?-)American in Planning Section 1)
Similarly, the characters of Women at Work:
Girl Next Door: Harumi Tanigawa (the brunette office assistant)
Tomboy: Akira Hayasaka (the russet-haired girl who is disguised as a boy-a false "trap")
Older Woman: Hiroko Miike (the meganekko project manager)
Maiden: Mutsuki ("Ojou") Oshima (the wealthy ojō-sama)
Alien: Minako ("Taka") Takahara (the muscled forewoman)
There is no Child character; Tomoko Kitazawa of Immoral Sisters and blonde May/Mei (the youngest sister) of The Story of Little Monica are good examples of this archetype in hentai.
For more on this subject, see "Stereotypes and Archetypes" on page 618 of Clements and McCarthy's The Anime Encyclopedia: A Guide to Japanese Animation Since 1917, Revised and Expanded Edition (Stone Bridge Press, 2006, ISBN 1933330104, OCLC 71237342), and the post "The Nolans System" (23 June 2009) on Clements' The Official Schoolgirl Milky Crisis Blog for the origin of this categorization.
1 McCarthy, Helen, and Jonathan Clements (1998). London: Titan (reprinted: Woodstock, N.Y.: Overlook Press, 1999). ISBNs 1852869461 (U.K.) and 0879517050 (U.S.A.). OCLC 44832651.
2 See also "zoku" in: Schilling, Mark (1997). The Encyclopedia of Japanese Pop Culture New York: Weatherhill. pp. 321-322. ISBN 0834803801. OCLC 36327417.
(Updated 11 August 2014.)