Castro agreed to join the Chinese Super League side on a season-long loan at the age of 36, after netting 147 goals for Los Verdiblancos over seven seasons.
The Spaniard fired the Andalusians to two promotions and now, after three consecutive seasons in La Liga, he has ventured abroad for the first time in his 17-year career.
“I’m only going until December so in a few months I’ll be back again,” Castro told El Correo.
“It is a new experience for me. I wanted to live abroad, I’ve been at Betis for seven years and now I’ve had this wonderful opportunity.
“When I return, I expect the team to be high up the standings and performing well as things are shaping up strongly for the season.
“Playing for this club has been a totally different experience for me than anything else.”