Reading through this for the first time and loving it so far. Poor Kiyomi, girl has made another executive decision that's going to blow up in her face. The sheer silence from most of the harem during the immortality discussion is telling.
On the topic of the future, I do hope the harem begins to plan ahead. Honestly, I hope Naruto chooses mortality because if the harem sticks around too long, people are going to notice. Even if the whole harem moves to a private island or some other location, laws of causality dictate that, eventually, a rumour would begin to spread about an "island of immortals".
Not to mention the potential of creating Orochimaru knock-offs who are interested in obtaining immortality for themselves. Simply put, the existence, or the mere rumour of an existence of an immortal family of shinobi, is going to create conflict. Looking forward to how this idea develops, but I am wary if the story starts to turn into, "then they lived happily and eternally".