When something planned for the future is pleasing and you accept the invite, you can say "Sounds good to me!"
E.g.
"Want to see a movie with me tonight?"
"Sounds good to me!"
You can also say "I'm in!" as a casual way to tell someone you accept their invitation to do something.
近い将来の予定されたことがうれしくて、誘いにのるときは、 "Sounds good to me!"（いいね！）と言うことができます。
例：
"Want to see a movie with me tonight?"
今夜私と映画見たい？
"Sounds good to me!"
いいね！
"I'm in!" （私も参加する！）も、何かの誘いを受けることを人に伝えるカジュアルな言い方です。
Sounds wonderful, thanks for the invite. I will see you there.
I appreciate the invitation, thank you. I'll be happy to attend the dinner.
It sounds like a great plan, I will definitely take you up on that offer.
When one invites you to a dinner or to any event for that matter and you are more than happy to go you may answer in the following ways;
Sounds wonderful, thanks for the invite. I will see you there.
I appreciate the invitation, thank you. I'll be happy to attend the dinner.
It sounds like a great plan, I will definitely take you up on that offer.
It is of vital importance to be polite and show gratitude in receiving the invite whether you plan on going or not. If you are not sure, you may always say that you will RSVP. RSVP is a process for a response from the invited person or people.
人からディナーに誘われたときに、ぜひ行きたいと答えるフレーズです：
Sounds wonderful, thanks for the invite. I will see you there.
（いいですね。誘ってくれてありがとう。そこで会いましょう。）
I appreciate the invitation, thank you. I'll be happy to attend the dinner.
（招待ありがとうございます。ぜひディナーに出席させてください。）
It sounds like a great plan, I will definitely take you up on that offer.
（いいですね。ぜひお言葉に甘えてそうさせてもらいます。）
行っても行かなくても、誘ってくれたことに感謝の気持ちを表し、礼儀正しくすることはとても大切です。はっきり決められないときは、「RSVP」すると言えます。「RSVP」は招待された人がそれについて返事をすることを言います。
The three sentences you see provided above are great ways to express to your listener that you accept their invitation to dinner. All three of these sentences are common in our everyday conversation and are common responses to invitations we are excited about. The last two sentences are appropriate for formal settings, like talking with our boss or giving a presentation.
Thanks so much for inviting me. I will definitely join you.
When accepting an invitation to dinner or any other function, it is good manners to thank the person inviting you and assure him/her that you will definitely join him/her. The word 'invite' functions both as a verb and as a noun. Here, it has been used as a noun in the first sentence meaning 'invitation'. In the second acceptance, it has been used as a verb.
So, you may say:
Thanks very much for the invite. I will be there.
or
Thanks so much for inviting me. I will definitely join you.
夕食やその他のファンクションへの招待を受け入れる時、その人に招待してくれたことを感謝し、彼／彼女にもちろん合流することを約束するのが適切なマナーです。「invite」という言葉は、動詞と名詞の両方で機能します。ここでは、最初の文では、「invitation」という名詞として使われ、2文目では、動詞として使われます。
以下のように言えます：
Thanks very much for the invite. I will be there.
（招待ありがとう。参加します。）
Thanks so much for inviting me. I will definitely join you.
（招待ありがとう。もちろん参加します。）
If someone has invited you to an event or special occasion, or even just a drink at a bar, either of these two answers are a good way of saying yes to the invitation.
All three answers are fairly casual ways of accepting an invitation.
"Of course i'll come. When and where?" - This answer is accepting the invitation whilst also asking details about the dinner/event
もし、誰かがあなたをイベントや特別なイベントに招待したり、または単にバーでの飲みに招いたら、これら2文のどちらかが、その招待を受ける良い言い方です。
3文全ては招待を受けるカジュアルな言い方です。
Of course i'll come. When and where?
（もちろん、行きます。いつ、どこですか？）
この答えは、招待を受け、ディナー／イベントについての詳細も聞いています。
Great, count me in!!!
This expression tells the person inviting you that they can include you in the number of people that will be attending. It's another way of saying you will go.
Yippee, I'll be there!
The expression 'yippee' is one of delight and wild excitement. This will show the person that you are not only happy to have been invited, but you'll attend gladly and willingly.
Great, count me in!!!
（いいね。行くよ！！！）
これは「参加者の数に私も入れてください」という意味です。自分も参加したいことを伝える言い方です。
-------
Yippee, I'll be there!
（いいね。行くよ！）
「yippee」は喜びや興奮を表す表現です。招待されてうれしいことと、ぜひ参加したい気持ちを表します。
When respoding to an invite you can use the simple/unformal approcah:
Sounds like a plan, Sounds good, Sounds good, Im in!, I will be there
You can also try something more formal:
I would like that
I would appreciate it
誘いに答えるときには、シンプル／インフォーマルにフレーズが使えます：
Sounds like a plan.（喜んで）
Sounds good.（いいね）
Sounds good, Im in!（いいね！行く！）
I will be there.（行く！）
もっとフォーマルに言ってもいいです：
I would like that.（いいですね）
I would appreciate it.（いいですね）
When you want to express that you think dinner with someone is a good idea and you're looking forward to it; then you can say it in the following ways:
-Sounds good. I'll be there
-That's a good idea. I'm looking forward to it.
-I'm in. See you then.
ディナーの誘い誘われ、それを受け入れるときの表現です：
-Sounds good. I'll be there
（いいね！行く！）
-That's a good idea. I'm looking forward to it.
（いいね！楽しみにしています。）
-I'm in. See you then.
（行く！後で！）
オーストラリア 
南アフリカ 
アメリカ合衆国 
イギリス 
