Name/Title at the end of a sentence. Vocative case?

Question

Consider these stanzas taken from the opening song of Aria the Animation: Undine.

Translations taken from this site

Background information:

• An Undine as a mythical concept is a female water spirit or nymph. In the anime "Aria", they are what gondola operators are called. (In layman terms they are boat rowers)

• Vocative case: the case used for a noun identifying the person or thing (animal, object, etc.) being addressed.

さあ　漕ぎ出そう　光る波へ

笑顔が　すぐ　こぼれる (Come, let us row towards the shimmering waves, our smiles will soon overflow.)

ねえ　伝えよう　このときめき (Hey, let us impart the feelings of our beating hearts. )

風にのって　あなたのもとへ

行くわ　ウンディーネ (Riding the wind, I will return to you as an Undine.)

---

さあ　漕ぎ出そう　遥か未来へ

水面に　夢　広がる (Come, let us row towards that distant future; our dreams will spread out over the water.)

ねえ　見つけよう　まだ知らない

宝物を　あなたと一緒に (Hey, let us discover yet unknown treasures.)

探そう　ウンディーネ (Together with you as Undines.)

I disagree with translation in the highlighted parts above.

(Question) Can it mean "Riding the wind, I will return to you, my Undine" and "Together with you, my Undine"? Treating ウンディーネ as vocative case?

Answer 1

I hadn't thought about the possibility of vocative case in Japanese, and your question provides an interesting point. The usage in your examples are clearly vocative, but it may not be that clear whether these expressions actually bear vocative case.

There is a group of particles called 間投助詞 (さ, よ, ね), which might be candidates for vocative case particles. Assuming that case cannot be stacked in Japanese (which is not necessarily true in other languages), the fact that you can stack さ and ね with が excludes the possibility that they are vocative case particles.

彼がさ、...
彼がね、...

We are left with よ, and you can attach よ to the relevant phrases in your examples. I suppose this is the vocative case particle. When there is no explicit case particle following a vocative phrase as in your examples, there should be several possibilities:

1. It is not vocative case. It simply lacks case. Since it is not an argument, a caseless noun phrase is possible.
2. There is underlyingly some other (default) case such as nominative, and is omitted.
3. There is underlyingly vocative case (which we can assume よ), and is omitted.

I don't think there is a consensus on the answer for this.