My Isekai Life: I Gained a Second Character Class and Became the Strongest Sage in the World!(2018)

Tensei Kenja no Isekai Life: Daini no Shokugyo wo Ete, Sekai Saikyou ni Narimashita

Whether at the office or at home, corporate drone Yuji Sano works all the time. So when his home PC flashes a message about him being summoned to another world, Yuji restarts his machine...only to find that he's inadvertently accepted the summons! Now in a fantasy world far removed from paperwork and computers, Yuji has just one thing on his mind: waking up from what he thinks is a dream and getting back to the mountain of work he left behind! But this other world has other plans for Yuji, who quickly discovers his Monster Tamer character class allows him to befriend slimes! And thanks to their number, those slimes help him absorb so much magical knowledge that he gains a second character class in the blink of an eye! How will Yuji wield his power now that he's the greatest sage the realm has ever known?! And what about all that paperwork?!

(Source: Square Enix)