https://book.dmm.co.jp/product/4237230/b915awnmg01783/
https://www.dlsite.com/books-touch/work/=/product_id/BJ640448.html

[Synopsis]

''Would you like to fall in love with me?''

Office worker Takahara Shunsuke suddenly finds himself on a southern island.
Shunsuke is about to start life on a deserted island with princess knight Elisa Phil Cromwell, who was found collapsed on the beach but she tells him that she has a mission to slay a dragon.
However, it's impossible for her to do so as she's only level 1...
However, he discovers that he has the ability to ''level up through love (sex)''...!?
He has sex with the petite, baby-faced princess knight alone on a deserted island...
She feels too much on her first experience and wets herself but then has a huge orgasm during a free-spirited, naked outdoor sex session!!
After learning the secret to leveling up and the good parts of sex...Elisa even invites him in!?
She gives a sticky blowjob with her horny sigh, a French kiss on top and a clean-up boob job and his sex level grows rapidly!!

This series includes episodes 1 to 6, depicting the two's lovey-dovey sex life on the island, from their first meeting.

Base +22