Chotto, sanpo-ni itte-kuru-yo. (I'm going to take a walk for a while.)

Situation 1: Mr. Shiba is about to take a walk.

夫：　ちょっと、じゅんをつれて散歩に行ってくるよ。

妻：　じゃあ、ついでにお茶を買ってきてちょうだい。

Otto: Chotto, Jun-o tsurete sanpo-ni itte-kuru-yo.

Tsuma: Jā, tsuide-ni ocha-o katte-kite-chōdai.

Husband: I'm going to take a walk with Jun for a while.

Wife: Then please buy a bottle of tea for me.

Today, we will introduce the various meanings and ways to use the auxiliary verb ～てくる. くる is originally the verb meaning "to come," and the pattern X (verb in te-form) +くる expresses this with an action(X), as in もってくる (to come bringing [something]) or つれてくる (to come with a person). In Situation 1, the usage of this pattern is different, expressing that a person goes somewhere, does an action (X) and comes back, as in Mr. Shiba's 散歩(さんぽ)に行(い)ってくる (lit. to go out for a walk and come back) and in Mrs. Shiba's お茶(ちゃ)を買(か)ってくる (to buy a bottle of green tea and come back) respectively.

Situation 2: At the office, Department Head Yamani is making a speech to her staff.

ヤマニ： わが社は、創業以来、人々の健康と内面からの美しさについて、真剣に研究し続けてきました。

Yamani: Waga-sha-wa, sōgyō-irai, hitobito-no kenkō-to naimen-kara-no utsukushisa-ni tsuite, shinken-ni kenkyū-shi-tsuzukete-kimashita.

Yamani: We have been seriously researching people's health and inner beauty since our company was founded.

The past form of くる is きた, and the pattern X (verb)てきた expresses that something (X) has been continually done from the past, as Ms. Yamani uses it in Situation 2. One more example: 私(わたし)は３０年間(さんじゅうねんかん)、このやり方(かた)でやってきたんだから、今(いま)さら変(か)えることはできない (Since I've been doing it this way for 30 years, I can't change it now). The words that mean continuation like ずっと (for long), 今(いま)まで (until now), ～つづける (to continue to do), etc. often go with this pattern.

The pattern X (verb) てきた is used to express the gradual change from the past to the present days, too, as in: このあたりも、だいぶ家(いえ)が建(た)て込(こ)んできたなあ (The houses around here have increased), or as in: 最近 (さいきん) ちょっと太 (ふと) ってきたみたいだ (It seems that I have been getting fat recently). In this usage, X tends to be the verb to express the change like ふえる (to increase), へる (to reduce), かわる (to change), ～なる (to become), etc., as in: 暗(くら)くなってきたから、早(はや)く帰(かえ)ろう (Since it's getting dark, let's go home soon).

Bonus Dialogue: Mr. Sere invites his colleague to eat lunch.

セレ： 三田(みた)くん、お昼(ひる)食(た)べに行(い)かない？

三田： ごめん、じつは今日(きょう)は弁当(べんとう)を持(も)ってきたんだ。

セレ： お、彼女(かのじょ)が作(つく)ってくれたの？

三田： 彼女なんかいないの、知(し)っているだろ？　姉貴(あねき)が作(つく)ってくれたんだ。ぼくがこの２週間(にしゅうかん)、失恋(しつれん)のさびしさに耐(た)えてきたから、ごほうびじゃないかな。

セレ： やさしいお姉(ねえ)さんだね。

三田： ふだんは全然(ぜんぜん)やさしくないんだけど、ぼくが失恋すると、やさしくなるんだ。きっと、姉貴も失恋ばかりしてきたから、ぼくの気持(きも)ちがわかるんだろうな。それにくらべて、セレくんはゆりちゃんとうまく行っていて、いいなあ。

セレ： ぼくたちだって、こわれそうになったことが何度(なんど)もあったけど、それを乗(の)りこえてきたんだよ。やっぱり、長続(ながつづ)きするには、あるていどのがまんが必要(ひつよう)だよ。

三田： ぼくも、そう思(おも)う。だから、ぼくはいつもがまんしているのに、相手(あいて)が全然がまんしてくれないんだよ。それが問題(もんだい)なんだ。

Sere: Mita, why don't we eat lunch out?

Mita: Sorry, today I've brought my lunch from home.

Sere: Oh, did your girlfriend make it?

Mita: You know I have no girlfriend now, right? My elder sister made it. I guess she's trying to console me, since I have been sharing my sadness with her for two weeks.

Sere: Your sister is so sweet.

Mita: Usually she isn't sweet at all. But she's sweet whenever I break up, because she has been broken up with so many times, I guess. I envy you because, unlike us, you and Yuri get along.

Sere: We have almost broken up many times, but got over it. You need patience to keep a long-term relationship, that's what people say.

Mita: I think so too. That's why I'm always patient. On the other hand, my partner never puts up with me. That is the problem!