From the Start, I Contracted Doraemon. You’re Saying He’s Only F-Rank?

Lin Yang has just finished the college entrance exams when he transmigrates to the parallel-world Blue Star. He discovers a world dominated by profession-holders, under threat from covetous alien races and on the brink of disaster. When Lin Yang awakens his profession, however, he unexpectedly becomes a Beast Tamer and contracts Doraemon, a character from a faraway anime world. Looking at the round blue cat in front of him, Lin Yang thinks he must be dreaming. Wait, you're calling Doraemon an F-rank contracted beast? You say only B-rank profession-holders can fly? No problem, I've got a bamboo-copter, so I can fly anywhere in the world. You say this is an absolute lockdown, and even SSS-rank, or god-tier, profession-holders can't escape? No problem, take a look at my Anywhere Door! The Time Cloth, the All-Purpose Pass, the Time Machine, the Devil's Passport... one bug-level gadget after another comes out, enabling the Great Xia Empire, teetering on the brink of ruin, to launch a counterattack right into the alien races' homeland. "In Great Xia, you call me Lin Yang. I won't hold it against you." "But here, what are you supposed to call me?" "Sing the praises of the omnipotent, almighty Holy God Lord Lin!" Lin Yang says this as he plants his foot on the head of the alien king.