The fun part about trying to reverse engineer an electric lighter is that if you accidentally bridge the wrong pins with your multimeter, you can start fires.
you slide the switch, which actually slides the external metal casing, revealing the business end, and turning it on. there's 4 lights on front to show you the charge.
There's a second PCB, which is just connected to the USB port on the other side of the battery. This one is USB-C, but with the way they designed it, they could have easily used micro-USB or lightning here.
So up above the main IC, there's a SOT23-5 chip labeled SKAF. That's a Natlinear XT4052 Standalone Linear Li-Ion Battery Charger with Thermal Regulation.
next to that is Captain Mystery over here, a "63ML" SOIC-6 or SOT23-6 SMD IC. No results for this on google. My guess is that it's another MOSFET or a DC-DC converter, but who knows.
so an interesting thing is that the microcontroller is always powered. it would make a lot of sense to have it turned on/off by the switch, but nope. it's always powered. I haven't measured the current, but I hope it has a low-power sleep mode.
And there's this mystery component here. I'm not sure exactly what type of component it is, but it seems to be taking in a voltage at about 4v and turning it into 44v. But the voltage is interesting!