Sono Monban, Saikyou ni Tsuki: Tsuihou sareta Bougyoryoku 9999 no Senshi, Outo no Monban toshite Musou suru

Sieg is an adventurer with an incredible defensive power, and he always uses himself to attract the monsters' attention to assist his teammates. However, the party leader just focuses on offense without realizing Sieg's intention, so he kicks him out. After Sieg leaves, the team repeatedly fails multiple quests...

At the same time, Sieg takes the position of gatekeeper at the Royal Capital. Thanks to his defensive power, he is quickly promoted to division captain. His subordinates include a carefree, big-breasted swordswoman; a perverse, freakish girl; and an archer with an erratic temperament. He and the girls start slowly gaining the trust of people around them!

(Source: Futabasha, translated)