Grammar Info
N4 Lesson 7: 16/18

お〜する
I humbly do, I am obliged to do, humble speech

Structure
Casual
Polite
+ Verb[ます+ する
(1) + する[Verb] + する

(1)
limited to [する]Verbs like: 電話する、勉強する、散歩する
+ Verb[ます+ します
(1) + する[Verb] + します

(1)
limited to [する]Verbs like: 電話する、勉強する、散歩する
Details
Register Polite
使用域 敬語
Information
お〜する comes from a form of polite speech in Japanese called 謙譲語(けんじょうご) (humble speech). This type of speech is used to refer to the speaker and their actions. This is opposed to 尊敬語(そんけいご), which refers exclusively to the listener and their actions. お〜する is almost exactly the same as お~になる, as in it simply means する.
お〜する is regularly used with words of Japanese origin, while ご~する will be used with words of Chinese origin. The する in this compound with attach directly to the ます stem of almost any verb.
  • 僕(ぼく)守(まも)りします
    I am going to protect you!
  • 今(いま)すぐに確認(かくにん)します
    I will check right now.
Caution
While the する in this structure will attach directly to the ます stem of verbs, this does not mean that verbs that are already する verbs will become しする. In the case of する verbs, simply change the prefix to ご.
  • 登録(とうろく)する方(かた)こちらクリックしてください
    For those who want to register, please click here.
  • 注文(ちゅうもん)する時(とき)こちらベル押(お)してください
    When you are going to order, please press this bell.
In rare cases, お may be used instead of ご, when attached to words of Chinese origin. There is no specific rule for this, and they must be memorized on a case by case basis.
  • 先輩(せんぱい)に電話(でんわ)するのがすきです
    I like to call my senpai.
  • 友達(ともだち)勉強(べんきょう)するのは楽(たの)しいです
    It is fun to study with my friends.
Thankfully, the words of Chinese origin that use お instead of ご are extremely common verbs. This means that you will be exposed to almost all of them very quickly. All others may be assumed to use ご.
Fun Fact
In the same way that お~になる is a more common variation of なさる (both 尊敬語(そんけいご)), お〜する is a more common variation of いたす (both 謙譲語(けんじょうご)).
  • 5分後(ふんご)に電話(でんわ)します
    After 5 minutes, I will call you. (I will call you in five minutes)
  • 5分後(ふんご)に電話(でんわ)いたします
    After 5 minutes, I will call you. (I will call you in five minutes)
Slow Male
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ドア閉(し)します
I (will) humbly close the door.
友達(ともだち)お母(かあ)さんパソコン借(か)しました
I humbly borrowed a computer from my friend's mother.
[⚠ While this is grammatically correct, 拝借(はいしゃく)する is more commonly used]
任(まか)します
I will humbly leave it up to you.
Online
Learn Japanese Daily
Tae Kim
Books
Genki II 2nd Edition
Page 189
[DBJG] A Dictionary of Basic Japanese Grammar
Page 42 & 360
Tae Kim's Japanese Grammar Guide
Page 230