“Do for somebody” is the opposite side of “do for me“, and they are both used extensively in Japanese (and Korean). “Do for somebody” is used when you do something solely for the benefit of somebody else:
- 何か食べるもの作ろうか？-> Should I make something to eat? (for you, or for you and I both, to eat)
- 何か食べるもの作って上げようか？-> Do you want me to make something to eat for you? (not for myself)
There are multiple “do for somebody” with different speech levels.
- 上げる (あげる) -> Neutral to informal
- 遣る (やる) -> Toward junior or rude, patronizing, dismissive
- 致します (いたします) -> Polite
- 差し上げる (さしあげる) -> Very polite
- 置く(おく) -> Neutral
Since やる、上げる can be very patronizing, they are only used between family members and friends, or purposefully dismissive statements.
- 誕生日にゲームを買って上げるよ -> I will buy the game for your birthday
- もう彼を許してあげたら？ -> Why don’t you forgive your boyfriend already?
- 私は毎晩子供の勉強を見てやる -> I oversee my kid’s schoolwork, help him/her learn, every night
- あんな馬鹿にくれてやる金など無い -> I don’t have money to give to an idiot like that
On the contrary 差し上げる and 致します are used almost always when you do something for your seniors/superiors, as both show respect to them while humbling yourself.
- 何か分かり次第御連絡致します -> I will let you know as soon as we know more
- 何か分かり次第御連絡差し上げます -> I will let you know as soon as we know more
- 私が御荷物をお持ち致します -> I will carry your stuff
- 私が御荷物を持って差し上げます -> I will carry your stuff
Unlike others, 置く is “take care of something for, on behalf of, somebody”
- あなたが病気で休みの間、あなたの仕事はやっておいた -> I took care of your work while you were out sick
- あなたの分は別にして置いた -> I set aside yours for you
- あなたのホテルの予約をしておいたよ -> I made a hotel reservation for you