I only just realized that this reincarnation/alternate Evin is technically an isekai. So we are in an Isekai in an isekai in an isekai. TRIPLE ISEKAI!! We are reaching levels of Light Novel as yet unknown to humanity.
Recommended age are a good indicator, not a bad idea to put a tag. Age restriction is only when you go official in the writting buissiness and publishers are liable under countries laws, as author you shouldnât care, unless self-publishing a book.