でごはんを全部食べきれないと思うがあります。そのときは、食べ始めてから残すより、先に「ごはんでお願いします」と言うが自然です。のでは、をときやを聞かれたときに伝えると、そのままます。
At a set-meal restaurant, there are days when you feel you may not finish all the rice. In that case, it sounds more natural to say, 'Rice, a little less, please,' before the meal starts rather than leaving it later on the tray. In many restaurants, if you say it when handing over the meal ticket or when they take your order, it goes through smoothly.
料理が来たあとで言っても、できるはあります。でも、すでに盛ってあると、が下げて入れ直すことになってしまいます。の混む時間だと、そのひと手間を避けたいもあります。だから、席に座って水を置いたあとではなく、のやり取りで短く言うがです。
Some places can still adjust it even if you speak up after the food arrives. But if the rice has already been served, the staff may have to take it back and portion it again. At busy lunchtime, some restaurants would rather avoid that extra step. That is why many people say it briefly during the first exchange instead of after sitting down with water on the table.
「ごはん半分」で通じるもありますが、量がによってちがうので、「」のが言いやすいことがあります。大盛りのでも、にするのは特別なお願いではありません。を渡す手といっしょに一言だけ足して、がうなずいたらそのまま待ちます。
In some restaurants, saying 'half rice' also works, but the amount of half can vary from place to place, so 'a little less' is often easier. Even in restaurants where larger portions are free, asking for less rice is not a strange request. Add one short sentence when handing over the meal ticket, and if the staff nod, just wait as usual.