Yu worked closely with Carson Yeung in ensuring his £81.5million takeover of the Blues went through last October.
He initially was given the role of vice-chairman of football and worked alongside manager Alex McLeish at the club's Wast Hills training ground.
But he switched to his consultant post in December and has had less of a prominent role at St Andrew's in recent months.
Yu told the Birmingham Mail: "I think the time is right for me to step down.
"After four years being part of the whole deal, from the beginning, I have done my bit.
"It's time to release myself and I wish Birmingham City the best for the future.
"To be part of the club's history in a very important era is a highlight of my life."