Manager Ange Postecoglou has already signed six Japanese players since the Australian swapped the J-League for Scotland in 2021. He had also been linked with a move for Oh's international team mate, Cho Gue-sung.
"I feel like I'm on a movie set and I'm really excited to be in the city and I'm looking forward to the upcoming days," Oh, who has penned a five-year deal, told Celtic TV on Wednesday.
"This is the moment I have dreamed of and I'm really excited to perform in front of the fans at the stadium."
The forward scored 13 league goals in 36 appearances for the Bluewings last season and earned his only international cap in November.
Oh becomes the third South Korean to have played for Celtic after former internationals Ki Sung-Yeung and Cha Du-ri.
"Ki Sung-yeung and Cha Du-ri are two of the players I respect the most. I have seen them playing for Celtic and I'm now happy to have the Celtic badge on my chest," he added.
Celtic have Japanese players Kyogo Furuhashi, Daizen Maeda, Reo Hatate, Tomoki Iwata, Yuki Kobayashi, and Yosuke Ideguchi on the books and Oh said he hoped he would settle in as well as they had.
"They will definitely be helpful because we have common things and as they have successfully adapted here I would also like to do the same," Oh added.
Celtic lead the Premiership by nine points from Glasgow rivals Rangers.