The teenage attacker only arrived at San Siro from Feyenoord last summer but he is now back in the Netherlands, having penned a four-year deal with the Enschede outfit
The Netherlands Under-19 international has penned a four-year contract with the Enschede outfit, just over 12 months after joining the Nerazzurri from Feyenoord.
Castaignos insists that he does not regret his decision to move to San Siro at such a young age but, having made just six appearances in Serie A last term, admits that he was drawn to Twente by the prospect of regular first-team football.
"I chose [in favour of the] certainty to play," the 19-year-old striker told his new club's official website. "Not that I am sure of a starting place; I must work hard. But I want to go back to basics and return to Netherlands.
"I realised that there was not much confidence in me [at Inter], yet I have no regrets."
Castaignos also revealed that he had initially sought out a return to De Kuip and also rejected offers from abroad as he had his heart set on going home.
"I wanted to return to Feyenoord in the beginning, but Inter would not cooperate," he explained. "There were a number of foreign clubs but I opted for Twente."
Twente were in the market for a new striker following Luuk de Jong's departure for Borussia Monchengladbach earlier this month.