Go somewhere to do something: Stem + に行く

Mental Model: The Arrow of Intent

When you travel somewhere to carry out a specific action—whether heading to the supermarket to buy groceries or flying to Tokyo to meet friends—Japanese fuses your goal directly to the motion verb using the purpose particle に.

Think of it as an arrow of intent:

• 1. The Activity: Boiled down to its pure action root (the verb stem or activity noun).
• 2. The Arrow (に): Points directly at that purpose.
• 3. The Motion Verb (行く(いく) to go, 来る(くる) to come, 帰る(かえる) to return): Propels you toward it.

Construction Formula: The Masu-Stem (連用形)

To build this expression, take the polite ます form of any verb and drop ます:

• Group 1 (Godan Verbs): 飲む(のむ) → 飲みます → 飲み → 飲みに 行く(のみに いく) (Go to drink) 買う(かう) → 買います → 買い → 買いに 行く(かいに いく) (Go to buy) 泳ぐ(およぐ) → 泳ぎます → 泳ぎ → 泳ぎに 行く(およぎに いく) (Go to swim)
• Group 2 (Ichidan Verbs): 食べる(たべる) → 食べます → 食べ → 食べに 行く(たべに いく) (Go to eat) 見る(みる) → 見ます → 見 → 見に 行く(みに いく) (Go to see / watch)
• Group 3 (Irregular Verbs): する → します → し → しに 行く (Go to do) 来る(くる) → 来ます(きます) → 来(き) → 来に 行く(きに いく) (Go to come — usually しに 来る)

The Activity Noun Shortcut (Zero-Masu)

For verbs that are simply Noun + する (such as 買い物する(かいものする) to shop, 勉強する(べんきょうする) to study, 散歩する(さんぽする) to walk), you can drop する completely and attach に directly to the noun!

• Department Store: デパートへ 買い物に 行きます。(デパートへ かいものに いきます。) (“I'm going to the department store for shopping.”)
• Library: 図書館へ 勉強に 行きました。(としょかんへ べんきょうに いきました。) (“I went to the library to study.”)
• Park: 公園へ 散歩に 行きましょう。(こうえんへ さんぽに いきましょう。) (“Let's go to the park for a stroll.”)

Both 買い物を しに 行く and bare 買い物に 行く are grammatically valid, but native speakers strongly favor the concise noun shortcut.

Combining Physical Destination and Purpose

When you want to state both the physical destination and the purpose, place the destination first: [Destination] へ/に [Purpose Stem] に 行く

• Sightseeing: 京都へ 紅葉を 見に 行きました。(きょうとへ こうようを みに いきました。) (“I went to Kyoto to view the autumn leaves.”)
• Study Abroad: 日本へ 日本語を 勉強しに 来ました。(にほんへ にほんごを べんきょうしに きました。) (“I came to Japan to study Japanese.”)

Stylistic tip: While Japanese permits using に for both the location and the purpose (京都に 見に 行く), repeating に close together can sound cluttered. Most native speakers instinctively use へ for the physical destination and save に for the purpose!

Purpose Formula vs Sequential Te-Form

A crucial conceptual distinction for learners:

• Purpose Formula (〜に 行く): One unified action driven by a goal. The trip only happens because of the purpose: 本を 買いに 本屋へ 行きます。(ほんを かいに ほんやへ いきます。) (“I am going to the bookstore in order to buy a book.”)
• Sequential Chain (〜て 行く): Two separate, consecutive events linked chronologically: 本を 買って、学校へ 行きます。(ほんを かって、がっこうへ いきます。) (“I will buy a book, AND THEN I will go to school.” The school trip was not for buying the book!)