The Japan international has scored twice in six games since joining Saints on loan in February.
But manager Ralph Hansehuttl has revealed there is no plan for his club to retain the 26-year-old.
"We don't even know what Liverpool thinks about the player in the summer.
"The deal was to give him game-time during the first half of the year when he is here.
"This is what we did definitely, until now, and hopefully he will get even more time to play."