I like the first paragraph. Just that making "that could be a problem" into "this could be a problem" would be better in my opinion. The first option feels more distant and less worrisome.
"Heaving a sigh, my hand clutched"
This makes it sound like the character's hand sighed, not the character themselves. Heaving a sigh, I clutched...would be better since you can use anything other than hands to clutch something.
The fight that ensued was difficult for me to follow, but I would get a second opinion on that part. I loved the line at the end where he curses before the second "click". It made me laugh haha
Again, heaving a sigh, I clutched would be better.
"Test over, this thing works wonders in battle."
I think "Test over--this thing worked wonders in battle" would be better in flow and tense.
I like how you showed the power of the watch instead of telling it. Good job! I will stop here. I think the problem with that is how little happened in the episode to attract me to the "villain". I like that he's clever, which we see a portion of in the first episode, but that's it. I hope my feedback was helpful.