Magical Girl Raising Project, (Light Novel) Vol. 14

An experiment gone wrong leads to the death of a famous mage, and the passing of this illustrious individual sends the Magical Kingdom into mourning. Then, a few
months later, the deceased mage’s relations receive letters from his proxy regarding the inheritance of his estate, inviting them to a tiny uninhabited island the mage had
used as a getaway cottage/research lab. When Mana gets one of these letters, she’s skeptical, but after careful consideration, she contacts two magical-girl friends to
accompany her there...