The variant of the image above, profile view of those two wearing underwear. Looking at this one...Chihiro's breasts are on par with Hinako's or they are a little bigger one of those two. It's one of those things that can be difficult to corroborate (remember, Gust never game measurements of the characters) but at least it's noticeable that Hinako isn't the only endowed character in the game, it's funny that Ako makes a big deal out of Hinako's breasts when Sanae, Rin, Chihiro etc...they have comparable chests at least, or even bigger.