The name of this concoction is deceptive for several reasons. It's not a cocktail 'partner,' since it already contains booze - it's just a 'cocktail'. Second, while it emphasizes its fruitiness, it only contains 2.8% fruit juice (if you're annoyed by 'fruit cocktails' in the U.S., Japan is ten times worse about that sort of nonsense).
And finally, this drink is only a partner to you, the drinker, in the sense that Ike was Tina Turner's "partner." While the initial sweetness may be beguiling, it's all going to get messy later.
The first noticeable thing is a bitter, tonic-y, almost medicinal taste. It's not overtly disgusting, it's just so utterly fake you'd be as well off pouring Everclear into Kool-Aid.
That said, I finished the whole can.