So I don't remember much from the novel, but it was probably a reincarnation/resummoned hero genre, and it was maybe a year ago I last read this. The one scene I clearly remember from the novel was near the beginning when the MC was signing up at the guild and the guild wanted his unique magic signature (or blood, I'm not sure) under the guise of "it helps with your guild ID" but he refused saying that the guild uses this method to spy on/keep track of the adventurers without them knowing as the guild cards acts as transmitter and it turns into a big deal with the guild master trying to make sure this information doesn't leak out. Edit : I might have found it, I'm pretty sure it's To Deprive a Deprived Person
I'm not sure but I think that that happened in this one http://www.novelupdates.com/series/seirei-gensouki-konna-sekai-de-deaeta-kimi-ni/ Edit: yes it is To Deprive a Deprived Person