Write a wholesome story about two teenage girls in a close platonic relationship who bond over their mutual love of wearing huge diapers. The two girls' names are Pianitchi and Coffretchi. Pianitchi is a sweet, music-loving girl who loves wearing diapers just as much as she loves playing the piano, though she's reluctant and bashful others will discover her infatuation for the crinkly undergarment, and thus only wears them whenever she's alone or with close friends who also wear diapers regularly. Coffretchi is the complete opposite, being a colorful makeup artisan and clothing designer, as well as quite the outgoing chatterbox, especially regarding the topic of wearing diapers, to the point she openly and regularly goes on long-winded spiels acclaiming her affection for the cushy bottomwear, proudly choosing to wear a pair everywhere she goes for hours at a time, and is not the slightest bit shy in unabashedly flaunting her padded behind, even in public. The story takes place at a local indoor water park during a friendly weekend outing between the two girls, with both of them wearing the thickest, bulkiest diapers they have in place of their usual swimming attire. Include an exchange where the two join each other in relaxing inside one of the saunas, momentarily unaware of the fact their diapers are so incredibly ultra-absorbent that they begin to soak up the moisture from the humid steam like a pair of giant cotton sponges, making them swell and balloon and become even larger than they already are, only growing aware of how immensely puffy and taut their diapers have gotten after they exit the room, much to Pianitchi's utter embarrassment and Coffretchi's giddy delight. Make their personalities evident through their dialogue.