Why would anybody step through a strange portal to beyond? You can't know where it goes until you step through. Then it's too late. Off you go to the surface of the moon without a spacesuit. How fun!
If your closet suddenly shimmered, and a portal to another world opened up, would you leap in shouting "Cowabunga!"? I'd like to think that I would, but I'd more likely be wary. "Hmm, I have a dentist appointment in nine hours. Maybe I can explore this convenient doorway to a world far from my bills and responsibilities next week on my day off."
The world of fiction is filled with stories where daring (or perhaps, clueless) people step into the fairy ring or climb into their wardrobe and undergo a new experience. It generally works out great for them. Nowadays, the main character would develop powers, fall into a harem, then save the world with all nineteen girls, each one madly in love with him. Compared to the isekai adventure, Western portal fantasies are so gloomy. If I stepped through that portal in my closet, I'd be sure to lie to the people on the other side. "Hey! I'm Japanese!" It's my foolproof plan for gaming the portal experience. I'd expect massive powers and a gaggle of beautiful women coming my way soon.
Occasionally, a story features a character who pays a price for traveling to their adventurous world. Urashima Tarō lost 100 years. Alice almost lost her head. Kirito was forced to make an extended stay. Sam Beckett bounced around time fixing people's lives, forever losing his own. Naofumi ended up with the short end of the stick and became reviled and hated. Sometimes the hero made bad choices, as was the case with Thomas Covenant, and sometimes bad choices were forced upon them. I'd like to think that Sharp will be joining their ranks, but he'll be gaining a beautiful companion, so perhaps no matter what trouble I create for him, it will all balance out.
—Dash