Ji, 20, assimilated from Chunnam Dragons for an undisclosed price as good as sealed a three-year stipulate during a Stadium of Light.
He has scored 6 goals in eleven appearances for South Korea, together with 4 during a Asian Cup in Qatar in January.
“I am so confident to be means to come to a good club, a good bar in a world’s series a singular league,” Ji told Sunderland’s in-house radio station, SAFC TV.
“I am happy since we have a possibility to plea a greatest players, as good as that gives me motivation.
“As a striker, we similar to to intimidate defenders. My target is to assistance a organisation get as most points as possible. That is what will give me satisfaction.”
Sunderland manager Steve Bruce said: “The child has been in illusory form for both bar as good as republic as good as he was a singular of South Korea’s stand-out performers during a Asian Cup, so we have been gay to move him to Sunderland.
“The Premier League is really opposite to a K-League, so there is tough work ahead, though we usually have to demeanour during players similar to (Manchester United midfielder) Park Ji-Sung as good as (Bolton winger) Lee Chung-Yong to see how good Korean players have been bettering to a gait as good as physicality.”
Gardner sealed from relegated Birmingham City upon a three-year deal, for a reported price of around £6 million ($9.6m).
The 24-year-old, who assimilated Birmingham from their arch-rivals Aston Villa, was a Blues’ tip scorer final deteriorate with 10 goals as good as was a partial of a organisation that won a League Cup prior to succumbing to relegation in May.