feel like its been shown from the various people that know him and can almost tell its him just from the feel/vibe that he ended up with such an inferiority complex that he simply doesnt realize that so many people trust and hold him in high regard, along with him being just being a genuinely good dude not noticing the extent of how much he helps people. that's 5 people so far that just had a feeling it was him from not a lot to go off of, with guild girl having the most thanks to the reports and talking to him. this is one case where i'm glad the titles wrong and all in his head, if they'd shown how much he helps people wanting basically nothing in return and he really was unwanted i'd be annoyed and ready for him to go full ghoul on assholes that show up xD. but he's managed to meet several nice and trustworthy people just because he's kind, endearing, and persistent. its not like he was suddenly experienced, dude learned and practiced for years and used that knowledge to help people, plus they already foreshadowed that many people of various lengths were originally guided by him in some way.
now i'm waiting on the now like gold, plat, or mithril, adventurer that once was helped by lento to pop up. it'd be pretty funny and epic if he does end up in trouble with the guild and people of various ranks and standing come out of the woodwork to defend him upon hearing his name.
edit: just read the rest of the comments here and, wowwee lol.
and to those asking/commenting about it a bit redundant to say, but , yeah those are the penalties if she breaks the contract, 1. she quits the guild. 2. she becomes specifically his slave.
i wonder if that was set up just to confirm or foreshadow that slavery exists in their world and is something in their location for a future plot point.