Celtic are expected to remain very busy in this summer transfer window. On the one hand, it is expected that the club will sign plenty of players in order to improve the squad. On the other hand, it has been suggested that key players like Daizen Maeda, Arne Engels and more could head for the exit door.

Of course, it is not new for key players to consider moves away from Celtic once the season comes to an end.

That happens pretty much every summer. Last time around, it was Nicolas Kuhn who made the move to Como FC. The year before that Matt O'Riley joined Brighton & Hove Albion. So on and so forth.

This is not expected to come to a halt especially in this summer transfer window, when it feels like a cycle has come to an end and the squad has stagnated a bit.

One of the players most likely to leave this summer is Reo Hatate, who seemed to be completely out of Martin O'Neill's plans towards the end of the season.

It was quite surprising, considering how highly Hatate has been regarded throughout his four-plus years at Celtic, even though his performances levels are shaky.

Even then, one would have expected Hatate to be involved in important games. But he was not.

Of course, if Hatate does leave, which is likely, most fans expect him to head to one of the top five leagues in Europe. But almost out of nowhere, it looks like a return to Japan could be on the cards.

According to Balon de Japon, an interesting rumour has begun circulating on Japanese social media. Hatate, who will leave Celtic, is reportedly on the radar of Kashima Antlers to bolster the J1 champions' midfield and reunite with Toru Oniki, who coached him at Kawasaki Frontale.

It remains to be seen if that ends up happening. Not many would have predicted that when Hatate eventually left Celtic, he would head back to Japan.

He does not look to be at peak form right now though. In fact, Hatate has looked a bit off colour for a few seasons now.

He was at his best when Ange Postecoglou was manager and did not even struggle at Champions League level.

READ MORE: Celtic Given Green Light to Make Move for World Cup Player

That had led to even feeling that it was almost inevitable that he would end up in the Premier League. For a while, it had looked to be on the cards as well. But that ship might have sailed.

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