This one is 2 volumes, but it does have what you're looking for in it. http://www.mangago.zone/read-manga/seven_days/
Oneshot. Childhood friend story
http://www.mangago.zone/read-manga/walking_with_you_junko/
Oneshot. Gay father realizing his son is gay too. It's a really nice story
http://www.mangago.zone/read-manga/hare_no_hi_asada_nemui/
Adorable story. Adorable uke x scary-looking seme
http://www.mangago.zone/read-manga/mayoke_no_darling/
I really recommend this. Story about two guys having the same interests. Friendship to lovers sort of story. One of my fav shounen ai
http://www.mangago.zone/read-manga/kimi_wa_natsu_no_naka/
Since you just want introductions, definitely shouene ai first. I would suggest
> What Lies at the end, a Korean webtoon
http://www.mangago.zone/read-manga/geu_kkeute_issneun_geos/?av=1
> Koimonogatari, this needs to be updated ;;
http://www.mangago.zone/read-manga/koimonogatari/
>Cherry Blossoms (this is a really cute must read! Might seem long but it's really not, but it's ongoing/ just ended 2nd season) http://www.mangago.zone/read-manga/cherry_blossoms_after_winter/?av=4
Others I would still out in but may seem longer than what you'd ask for
>Fools, another webtoon
http://www.mangago.zone/read-manga/fools/
>one of my all time favorite shounen ai, still ongoing and there's a lot of characters, lengthy
http://www.mangago.zone/read-manga/moon_trick/
>Circle, a Chinese manhwa, ongoing, pretty angsty. Beautiful art.
http://www.mangago.zone/read-manga/circle_wang_zi_ying/
> http://www.mangago.zone/read-manga/heesu_in_class_2/?av=1
I totally agree on Koimonogatari (and the others as well, but especially that one). I think it's an excellent first-time shounen ai, for the simple fact that one of the MCs has just found out a classmate is gay, and then proceeds to address each of the social prejudices against gay people that he has simply, until that point, assumed to be true, only to realise they're not. And then the other MC is the aforementioned gay classmate, and the story deals with the issues he has to face in accepting his sexuality. The only downside with this one is that it isn't finished. Can't wait til it is! One of my all-time favourites! :)
CBAW is also a good first-time shounen ai, because it's just so darn cute! :)
Other possibilities, though slightly longer and/or not yet complete, are the webtoons Star x Fanboy, Heesu in Class 2, and Here U Are.
And the manga Doukyuusei, which is also available as an anime film. The film was what got me into BL, actually. :)
Links to the above:
http://www.mangago.zone/read-manga/star_x_fanboy/
http://www.mangago.zone/read-manga/heesu_in_class_2/?av=1
http://www.mangago.zone/read-manga/here_u_are/
http://www.mangago.zone/read-manga/doukyuusei_nakamura_asumiko/
Excellent suggestions there! And some new ones for me too, yay, can't wait to check them out! I totally agree about Furuya Nagisa's stuff, really good.
Ichikawa Kei was one of the first authors I read when I started reading BL. Slow Starter was the first, but Blue Sky Complex became my favourite (more yaoi than pure shounen ai, but perhaps a good bridging manga to read if wanting to go from shounen ai to yaoi).
A couple others I thought of:
Yorimichi http://www.mangago.zone/read-manga/yorimichi_kazuki_rai/ (oneshot)
Hatsukoi http://www.mangago.zone/read-manga/hatsukoi_kazuki_rai/
Both of those by Kazuki Rai who also does Haikyu!! djs (it shows in the art!)
I want to get my friend in the yaoi world but I don't wanna shock her too much. So can someone recommend me a good manga, not too long (just one volume) and without sex scenes. Of course, they can kiss and the sex can be implied, but not really showed.
Thanks in advance!