"Hina-chan's Big Trade! Millionaire Lunch" is an adventure game where you trade all sorts of items with various characters in order to gather lots of food.

With no offers to be in the mainline games, Hina-chan, AKA Kagiyama Hina, has finally gone broke.
When she looks in her fridge to prepare lunch, she finds nothing but a single cucumber.
However, she doesn't let her misfortune get her down and comes up with the idea of trading her cucumber away to a friend, and then taking whatever she gets and trading it again -- working her way up to a lavish lunch like in the tale of the straw millionaire.

By searching around and talking to other characters, you can find and be given different items.
Then, by showing those items to different characters, you can trade them for new ones.

Gather as much food as you can before lunch so you can have a nice, rich meal.

The quality and amount of food you get will change your ending. Keep trying and aim to achieve the ultimate lunch!

Your trade partner won't always trade you for whatever you show them, but they'll always give you some sort of response regardless.
Forgetting about lunch and just seeing reactions and making small talk can be fun, too.