Stray current can’t be good. I am using a Twinstar device that is similar and have my hand in the tank many times with it running without any such issues.

 

Would you be able by any chance to check with a multimeter if there is no stray voltage leakage please? As you might be not aware of any stray current in your tank as far as you don't have any wound on your skin.

 

I believe this is one of those devices that electrolyze water, though I feel that its claims are questionable and outlandish at best, and completely false at worst.

That being said, stray current is never a good sign, so in the interest of safety, it would be best to remove it.

 

So I got a multimeter and I found out that this device generates 3V stray current in my aquarium. If I did not cut my nails too short I would not realize there is a stray voltage leakage in my tank.
I sent a message to Chihiros support but they did not reply yet. I have also messaged the shop where I got the device and they told me they have never had this issue. Now I don't know what to do, perhaps I can try to change the membrane. I liked the device it makes the water super clean.

Also I asked about the issue in Aquasabi and they said its normal:

Yes, this is quite normal. Of course there is electricty in the water, when the sterilizer ist active. If you have a wound or sensitive area on your skin, you may feel it. But this will not harm fish or plants, because the amperage is very, very low (mV).

 

Measured 6.4V AC without the Twinstar plugged in (but with canister running) and 6.6V AC with the Twinstar actively running. DC voltage was negligible both times 0.0020ish. Glad you figured it out. The Twinstar is velcroed to the side of my tank but it doesn’t get wet. Not much anyway.