The story is about a protagonist and his childhood friend who are summoned to another world, exploring and investigating, and getting into some naughty situations while trying to return to their original world.
Another World Childhood Friend: A story about a childhood friend who calls me her big brother and gets into some naughty situations!? [ganbara9]
The main story is linear.
By repeating the story from there, events occur that change and there are sub-events that are separate from the main story.
You move around the map like in an RPG to advance the story, but there are no battles.
I don't think there are any difficult strategies, but the ending changes depending on your choices and certain numbers.