In his ending for Fatal Fury Special, he seems to have overexerted himself and is hospitalized. This scene is most likely a callback to the first OVA since he is fine throughout the rest of the series. He decides to live the rest of his days in retirement and he occasionally enters a competition to keep in shape. Though he taught Terry for a time, Tung made it a policy to refuse any other disciples. He seems to break this in Real Bout by apparently making the Jin brothers his apprentices. Some endings in Real Bout 2 show him taking only Jin Chonrei as his apprentice though, with Jin Chonshu staying with Kim Kaphwan.
Role in Super Smash Sisters
Tung Fu Rue is an NPC helper in Smash Sisters. He is an elderly man who carries his moves over from the Fatal Fury series. Whenever he pumps up and rips through his shirt, he risks fighting shirtless for the rest of the fight.