Ningyo no Namida

Hero goes out looking for the bride in a fantasy world. He meets different characters and animals and talks to them to solve their problems.

This game is a often mentioned in the subject about what was the first doujin software.

Some claim that this game is the first doujin software
Some claim that such software (unofficial software made and sold by individuals or small groups as a hobby) existed even before this work, although it was not called "doujin software".

However, at least it seems certain that this game is the first software called "Doujin Soft".