Maybe try,
1) Hidamari Ga Kikoeru
2)Tsumasaki Ni Kourozu
3)Sayonara, Heron
4)Nouka no Muko
5) Hana To Usagi
6)Merry Checker
7)Koisuru Barairo Tenchou
They are less fast paced, but I'm not sure they have the exact same feel, but I think you still can see relationships build. Let me know if you've already read them, or think they aren't what your looking for. Good Luck!!
I felt the same so i created a list i could go back to whenever i'm tired of my purely smut reads.it's my "takingnforever" list http://www.mangago.me/home/mangalist/47826/?filter=&page=1

Well yeah...I've read many yaoi manga now and I just want a yaoi/shounen ai manga with slow plot like Slow Starter (Ichikawa Kei), did you guys have any suggestion? ╥﹏╥
I'm getting tired with a cliche plot :v Like seriously the uke/seme fall in love in 1 or 2 chapter and sometimes with force or sex force -_-