After the conclusion of the last arc, MC got forced to join as an S rank hero in the next human country to be destroyed. And to prove his legitimacy for the rank, he went straight to a high level dungeon and got is ass kicked.
That he got beat instead of one shotting everything shows this is shounen first before isekai/reincarnation.
Correction, he joined the Sun Cult to pay back Crimson for aiding Ria and the rest. As soon as he arrived got hit straight in the face with his Karla phobia, then inmediatly after by his enoclophobia standing before 1 million believers that saw him as a God's Miracle.
And after that he should be meeting with the rest of the Dragon Slayer Monks, but he already reached his limit and said "fuck this Im out, Ill get rid of the Bloodline of Breath/Roar to compensate for skipping the meeting" due to his phobias xD
Still he performed quite well, considering that seemingly only the Rank 2 and the King were a real threat to him (the King atacked him already in Dragon form) and survived despite going yolo against the Bloodline.
Dont forget that this Ragna is not on the same power than when he faced Kamui, since Ria's blade was shattered and now is only using the remaining hilt. Kamui was stated to have a chance to beat any King but Gilzea and thats before achieving his Thunder God form