Indoor Cat vs. Outdoor Cat
In general, l feel that letting cats go out greatly shortens their lifespan. (And worrying about why they didn’t come home will shorten yours.) The greatest danger seems to be cars. In spite of that, we do allow some of our cats to have an inside/outside life. We have some cats that were likely born outside and grew up outside. Though they have gotten friendly with us, even sleep on our bed sometimes, they have not tolerated inside life very well — or got along with other cats in an inside-only community. We felt our only choice was to allow them outside.
If your cat has not yet tasted the pleasure of the world beyond the genkan, I would not let them out. Instead, find ways to bring the outside in. Cut them some grass or green bamboo stalks and leaves. Watch them eat it up, and then likely vomit it out to clean their stomachs. Get a concrete block and leave it outside for a couple weeks. Bring it in, watch your cats sniff and rub against it. Give them a place in the sun or an open to air window to enjoy inside, that they can not escape from. If you have a veranda or a little garden space (lucky you!), look for ways to enclose it. You can give your kitties a little piece of paradise: include a dead tree to climb, remove dirt cause they will certainly do their business there.
If you have other ideas, please share them in the comments.