I have the same question.
The latest chapter IS chapter 12. The missing chapter 11 is the end of the last mission where Yamato gets his dislocated shoulder fixed and there is concern about how much he's willing to sacrifice his own safety, Sougo vows to train more to be able to protect his friends and teammates, and Tamaki feels up Yamato in about the most action you get to see for a while ;)
Volumes 4 and 5 are basically all backstory where Sougo and Yamato are at school. There's not much BL goodness but a lot of plot.
do you have any idea with whom yamato ends up with?i hope with tamaki.....
with nobody, at least until Volume 5.
where are ch.11 and 12....????????????????