These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
In Chapter 10, Ryoko starts revealing embarrassing secrets about Yuki to Tsuruya, who does the same with Mikuru. Tsuruya then reveals that Mikuru has a star-shaped mole on her chest, which is something that Mikuru did not know before and is greatly embarrassed. Now, in Ryoko's case about catching Yuki checking her weight after a shower makes sense, since she's a close friend who frequently visits her, but, for Tsuruya to be the one to know about Mikuru's beauty mark is, while funny, a little strange, since it's not really explained how she knows...Not to mention that Mikuru looks seductive in that page.
When discussing Valentine's Day, Mikuru says she would be happy to get chocolate from Yuki if Yuki were male, and sheepishly admits that it came out like a confession.