How do you say since when in Japanese?

Answer 1

Casual: okaeri (oh-kai-eh-ree) おかえり　（お帰り）

Polite: okaerinasai (oh-kai-eh-ree-nah-sigh) おかえりなさい　（お帰りなさい）
The most common phrase used to welcome someone home is:

Okaerinasai (おかえりなさい)

This is normally said in response to (or replied to with):

Tadaima (ただいま) ("I'm back/home!")

welcome home is okaerinasai
To greet someone who has returned, you may say 'okaeri.' "Welcome back best friend" is sort of awkward, and I don't imagine that would occur very often in Japan. A simple, enthusiastic 'okaeri!' should be sufficient. It is written: お帰り

Answer 2

"Since when?" is "itsu kara?" (ee-tsoo kah-rah).

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Let me add a few more examples "since" the explanation could be a little complicated. :)

1.When "since" is used as a conjunction to show the intervening period between the time mentioned and the time under consideration, typically present, see the example below:

I've been in touch with him since I was sixteen.

わたしは、１６さいのときから、かれとれんらくをとっています。

(Watashi wa juu-roku sai no toki KARA, kare to renraku o totte imasu.)

"Since" is translated into Japanese as "〜KARA (pronounced KAH-RAH)" in this case.

2. When used as a preposition, you can say, "〜KARA", too:

It's been raining since morning.

あさから、あめがふっている。

(Asa KARA, ame ga futte iru.)

3. As an adverb, you say, "〜KARA" or "〜IRAI (pronounced EE-RHA-EE)"

He left home last Saturday and we have not seen him since.

かれは、せんしゅうのどようびにいえをでて、それから（いらい）わたしたちはかれにあっていません。

(Kare wa, senshu no doyoubi ni ie o dete, sore KARA(IRAI) watashi tachi wa kare ni atte imasen.)

4. As a conjunction to show a reason, you say, "〜DAKARA"

Since we're friends, we'll go dutch.

ともだちだから、わりかんにしよう。

(Tomodachi DAKARA, warikan ni shiyou.)

Answer 3

oraen maniya

Answer 4

Hisashiburi