Kyogo barely featured despite the Ligue 1 side forking out £10 million to land him and he was eventually sold to the English Championship side and made his league debut in a 1-1 draw with Ipswich Town on Friday.
And, in an interview in his homeland, Kyogo admitted he struggled both with the physicality of the French league and with communication problems.
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He said: “I found the French league more physical than in Scotland with Celtic.
“The manager told me I had to adapt and find a way around it.
“But when I am frustrated in Japan, I have people I can talk to. In France, there was no one.
“I didn’t have an interpreter like I was used to and that didn’t help either. I studied French for six months, but I don’t think I got anywhere with it.
“It’s so important for me to be playing games now with the World Cup less than a year away. It will come around quickly.”
