after they leave the base (that was built by Zepairu (the one who summoned Rei) and his comrades in the middle of forest that after 1000 years got quite big, of course Zepairu and rest are long dead) the first thing they need to do is to leave the forest, find human settlement, get some food. Standard (they kill water bear and Set eats its crystal and learns new skill) So they leave forest and find human city, Rei realizes that griffin is A rank beast, everyone is scared of Set.
Some way or another Rei and Set enter the city and Rei registers with adventurers guild (of course he start at the lowest rank, since you know… no one ever start at the top. So the ranks are from top to bottom: S, A, B, C, D, E, F, G and H. At H rank you are not allowed to take missions outside the city and in order to rank up you need to prove that you can somewhat fight.) and during registration drunken D-rank party of 4 adventurers pick makes fun of him, so he pick a fight with them and uses it as opportunity to prove that he can fight. (they underestimate him because of his young appearance (he looks like 15) and the fact that he just registered. Needless to say that it’s very rare in that world for strong people to not be already registered in the guild or to not be known.) So they fight one-on-one and he beats them without trouble and ranks up to G-rank. (As a note D-rank isn’t anything very strong, the normal orc is D-rank monster in this world while goblin is considered to be F-rank)
The reasons why he joined the guild are magic crystals (Set and Rei’s weapon can absorb them and learn skills if the beast that crystal came from had a skill), informations and money. Rei might be hiding some of his strength and skills through the story but by no means he tries to look like a weakling. (and let’s be honest anyone who would just go and show off his whole strength to everyone is a complete moron. It’s always pays off to have some hidden cards. Especially in the world filled with monsters and conflict.)
So Rei and Seth do some subjugation requsts, gain some skills. Then there comes emergency request, the orc village was found 2 days from the city. Adventurer Guild organizes a subjugation party with ~30 people total. Naturally Rei and Set also join. So they make some friends and Rei kills Orc King B-rank monster in one-on-one fight. Ranks up to E-rank and is informed that soon the D-rank exam will be held.
So the D-rank exam turns out to be bandit subjugation. There are 5 other people who also are taking the exam.
Rei ends up as the leader because his social skills are poor (the examiner appointed him as such) and Set isn’t allowed to go with them because he is to strong for D-rank exam. (the goal of the exam is to see if they can handle killing other humans). They pass exam without much trouble (2 warriors, mage, spirit archer, thief and Rei are just an overkill for bandits.)
And after ranking up to D-rank Rei receives nominated request from the lord of the city to be part of the escort of Duke daughter who is going to go to the labyrinth (she is also B-rank adventurer)