Into the Creations

After returning to my room, I examined the key I had obtained from the prison.
It was a black key about 10 cm long, with a red gem embedded at the end.
Of course, I knew how to use the key from the original story.
'Press the red gem at the end of the key and twist it into the air as if inserting it...'
The red gem at the end of the key began to glow. It was proof that it was working. I twisted the key I had thrust into the air.
The space around the key began to distort, and a white portal shimmered into existence.
'Success.'
The key to the ancient warrior training ground.
This key opens a portal to an artificial dungeon used as a training ground for warriors during the ancient civilization era. The portal lasts for one minute.
Once the portal is opened, it can be opened again after 12 hours.
In the original story, Kyle trained inside this dungeon. Training here is slightly more effective than training outside.
'Let's give it a try.'
Without hesitation, I stepped into the portal.
'Oh!'
The training ground came into view.
What I saw was a clear blue sky and a training ground carved out of rock. The training ground was incredibly vast, with green trees planted here and there. Beside it, a stream of clear water flowed quietly.
It looked exactly as described in the original story. By the way, no living creatures inhabit the stream. The water is drinkable, and you can even bathe in the lake downstream.
"This entire space is mine now."
I grinned and headed toward the training ground.
A clear female voice echoed from all directions in the training ground.
I wasn't surprised since I already knew about it.
"Yeah, nice to meet you. But who are you?"