The Japan attacker spent the second half of last season on loan at St. Mary's.
"It is never nice for a player when you don't end up getting the game time that you want to have, when you only train and are not see as part of the first 11," Hasenhuttl told Hampshire Live.
"This definitely then helps your mentality when you later get a lift and a chance to play.
"Players like to join big clubs because they get a lot of money there and they get a lot of praise for being a part of the top six, if you will.
"But it is only for a short moment that you are happy about it because when you are not playing enough times and you are not important for the club, then it feels very awful, very quickly.
"The most important thing for him is that he gets a chance to play. We had so much rotation with injuries and everything that it was clear he would get a lot of game time with us.
"We have had talks with them and they are not so sure what will happen with him because Liverpool may make some things happen in the transfer market.
"For him, it was important to play here. We gave him that chance to play and we have enjoyed having him here."
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