Ah, Shuu - my first love. :)
On the last page, top right - I don't have that one either, so I know it's one you only get if you don't have a pet and keep visiting Shuu during the days. I've seen the pic, and it's adorable.
On the second page, the one on the right I got by having him be dominant - and apparently had sex with him a few times, I remember seeing the developer comment here - and using my mouth on his penis three times in a row. The one on the right, I got by having him top our first time. Don't know if you get it otherwise.
Hope that helps!