Mezase My Home! ~Niizuma o Mamore~

Rentaro is a salaryman. He hears rumors about a beautiful girl on a train, so he takes the same train. He meets Erika there and falls in love with her at first sight. Surprisingly, girl agrees to go on a date. But Erika's father refuses to recognize seriousness of relations unless there is a wedding, a house and a common child. Protagonist promises to become worthy of Erika in two years time.

[From vndbreview]