Vertical left angle bracket

It opens an angle bracket in vertical Chinese or Japanese text. Chinese and Japanese can be written in columns read top to bottom, right to left. In such columns brackets turn a quarter, so 〈, which points left in a line, points up: that turned shape is ︿, and its partner ﹀ closes the pair.

The single angle brackets 〈〉 have their own jobs. In Chinese as written in Taiwan and Hong Kong they mark the title of an article, chapter, poem or song, while 《》 marks a whole book; in mainland usage 〈〉 marks a title nested inside another title. Japanese writers use 〈〉 to set off a term or add emphasis.

Modern layout software turns ordinary brackets by itself. ︿ exists as a separate character because older East Asian character sets, such as Taiwan's Big5, stored vertical punctuation as ready-made shapes, and Unicode kept them so old text converts without loss.

Why does it turn up in kaomoji and as an arrow?

Because it looks like a small roof or caret. Out of vertical text, ︿ is simply a handy shape. Pairs like ︿(￣︶￣)︿ turn it into two arms raised in a relaxed "whatever" or a cheer, and some people use a lone ︿ as an up arrowhead or a decorative peak.

That works on screen, but the character is still a bracket. Screen readers may announce it as one, and some search tools treat it as 〈. For an arrow meant to be read, ↑ or ▲ is the clearer choice.