Keitaro Konnai was born on 1978-08-05.
Keitaro Hoshino was born in 1969.
Keitaro Harada was born in 1985.
Yes He does
Keitaro Miyamoto has written: 'Kaburimono kimono hakimono' -- subject(s): History, Kimonos, Japan, Boots and shoes, Costume
Yes
It's a toss-up between Keitaro Urashima and Naru Narusegawa
The cast of Thinking Dot - 2012 includes: Keitaro Oshima
Keitaro Azumi has: Played Sgt. Suetaka Kawakami in "Ashita e no yuigon" in 2007. Performed in "Shimokita surouraifu" in 2009. Played Daisuke Teshima in "Hikensha G" in 2009. Played Resistance in "Higanjima" in 2009. Played Shinji koyanagi in "Doubles: Futari no keiji" in 2013.
The cast of Kane - 1967 includes: Yukio Aoshima Keisuke Ishizu Katsuhiko Matsunami Keitaro Miho
Both Mutsumi and Naru. Keitaro remembers his promise with mutsumi, but he made a promise with Naru first. However, the other girl is unknown.
The cast of Moka wo kugurite - 1926 includes: Keitaro Machida Taisuke Matsumoto Shizuko Ozaki as Oishi Hiroshi Sakurai Ranko Sawa as Tomie Chieko Sugimura as Tamiko
Sure it's possible. How "annoying" they are depends on your personal feelings about the object of their ... well, whatever phase they happen to be in at the moment and how much you want the relationship to succeed. If you really really want Keitaro and Naru to get together, then you're likely going to be more annoyed with her at the early stages and less so later. If, however, you're a Keitoko shipper, it's likely to be the reverse. If you don't particularly identify with Keitaro or care who he winds up with, then him getting punched is mostly just funny regardless of who's doing it. So one way to make them "less annoying" is to avoid One True Pairing status, and make every potential relationship seem about equally "desirable".