I don't get yokozawa and kirishima's relationship i mean in the ova yokozawa takafumi no b...

I don't get yokozawa and kirishima's relationship i mean in the ova yokozawa takafumi no baai they were kissing and stuff but in the manga there was not even a single kiss i can't find the first chapters of the story i mean the chapters of the ova and their relationship's not clear not even a single kiss in the manga what are they then!! Or do they have their own manga or what i'm confused cz i liked them in the ova