Boku to Go-nee to Umi no Year!!

You play as the grandson of an egomaniacal high-rolling real estate agent. Through his business, he has made connections with many a powerful person. He has recently taken ill and has sent for you to see him. Gladly leaving your dull private school life for a little bit (summer break), you gladly head over to his estate where you used to spend vacations at. Upon your arrival, your grandfather gives you his final orders: to produce a grandchild for him. This should preferably with be done with one of five daughters of a man with a sizable (and highly desired) piece of land. If you succeed, you will become the president of his company. Your failure will result in your deportation to a life at a US military boot camp. Sounds like you better not screw this up!

[From White Masq]