This is going to sound so freaking wrong, creepy, anything bad you may want to say but oh well. I still have 2 stories
I went to a boarding school for 2 years back in 2010 and there was a "closet" room where guys could leave their bags if they had no space inside their personal lockers, most were empty, others had used clothes, others were clean, etc.
I should mention, this boarding school wasn't very good, it was kind of unsafe because most of the time something was stolen, cellphones, shoes, pendrives, etc. very important material things and if a student was caught he wouldn't be allowed to live at the boarding school anymore, me taking underwear was
waaaaay too little and unimportant compared to the other things other guys stole all the freaking time. Morality be damned, I had important things of mine stolen too so I gave no fucks during the time I was there and the ambient didn't help the general attitude there.

Well, moving on, my used underwear fetish was raging more than ever and if I liked guys, I'd always find a way to take their used underwear from their lockers when nobody was around (or I would take them from the storage closet room), some didn't even use locks and the ones who used locks, well, all the locks were shitty there so they were easy to open. Most of the guys kept their used underwear in plastic bags or they just left it there, but I would rarely stole more than 1 piece of underwear per guy and I only took undies from like 3-4 guys in those 2 years, I prefered to jack off with their undies and return them to not raise any suspicion... so I wasn't such a bad guy after all
The other story, I'll just copypaste from another thread:
2 years ago while I was studying away, I rented a room in a small apartment owned by a couple (they liked to go out a lot so we were alone most of the time) and a straight guy rented the other room, we became friends shortly but he didn't know about my sexuality, I started finding him hot over time and whenever he was away, I snuck into his room and took all his underwear to jackoff (sniffing aaaall his boxer briefs during each jackoff session, I jacked off on his socks but making sure I never cummed into them... except for one time I didn't react on time and filled it XD but every weekend he sent his dirty clothes to the laundry and didn't check it before so he didn't know.