The defender has also declared he needs 'time to forget about football' after the Samurai Blue were knocked out on penalties.
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Japan had one foot in the quarter-finals after they led their European opponents 1-0 going into the break courtesy of Daizen Maeda's close range strike
But Ivan Perisic equalised in the 55th minute with a header into the far corner.
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And with both teams failing to create further chances, the last-16 tie went to penalties, with Japan missing three out of their four spot-kicks.
Victory for the Asian nation would have seen them reach the quarter-finals for the first time in their history.
Tomiyasu failed to contain his disappointment following the match, as he said: "Of course, we are so disappointed with the result.
"My performance was a disaster today so I am sorry for the team.
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"I just need to be much, much better to help the team. It was not enough and also for the team, we did not deserve to win.
"We were so close to achieving our aim. They were better than us."
He added: "I can't be proud. I am not satisfied about what happened.
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"This is football and we need to be much, much better to win against a stronger team."
Attention for Tomiyasu will now turn to Arsenal ahead of a busy second half of the campaign.
But the ex-Bologna right-back has insisted he needs to have some time away from football after being asked whether he will link up with his teammates in Dubai for their warm-weather training camp.
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He remarked: "I don't know. Hopefully, I can get a bit of rest. I need time to forget about football. I need a bit of time."
Tomiyasu has struggled for injuries this season, with the 24-year-old's first start of the World Cup coming against Croatia.
He was eased back into the team this term following a calf injured sustained towards the end of last campaign, with his first start in the Premier League coming in the 3-2 victory against Liverpool on October 9.
But he then picked up another muscular injury which saw him miss the last three matches before the international break.
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