/jp/ - Otaku Culture

Why, though?
Even disregarding how breathing masks and magic toys designed for use on the surface are very different from scuba masks and water breathing, it's obvious that the original item was meant as a reward for getting close to Wakasagihime.
The concept behind it would then be that progressing with Wakasagihime would eventually unlock access to her home, serving as a milestone in the relationship. Unlocking that from something unrelated would only undermine that part of the gameplay loop and make the reward redundant, making it far less satisfying as a result.