Dunno if there's an existing tag to identify a front-tied bikini top...

Well, the side-tie part refers to the bikini bottom of course, most side-tie bikinis are also front-tied for the top.

Heh, now that's a great way to waste time in the new year - taking stats for side-tie bikini vs. front-tie tops. :-) :-)

From only a short (but very pleasant) survey of Danbooru posts tagged with side-tie_bikini, I would say that Piespy's assertion is perhaps a little premature or less-than-conclusive. I have seen a number of different top types:

- solid fabric band between breast cups
- entire front is unified (e.g. tankini)
- string between cups, tied behind neck
- string between cups, wrapped around neck then tied in front of neck
- metal loop between cups (ornamental only; tied hehind)
- bowtie in front (ornamental only)
- bowtie in front, actual attachment

That's not to mention the cases where the usual bikini tops are actually replaced with shirts, jackets or other garments. So...