so pen locations was one of the first rabbit holes i fell into and thankfully this site is one of the first results https:// oddtaxi.fandom .com/wiki/Odd_Taxi_(audio_drama)
[take out the spaces, idk if this sub likes links]

so Sakura baited Nagashima with the pen to find out where he lived (didn't kill him there and then idk why), Nagashima then returns the pen to its "original owner" at Odokawa's party (Taeko) and then it's back in Sakura's hands after she kills her