Ichigo 100% East Side Story is nothing more than a short story with some of the characters from the original story, a couple years after it's ending.
If you've finished Ichigo 100% and want a little bit more of it, you might as well give this a check, since it's only 4 chapters long anyways.
Having in mind that this was released a good 12 years after it's parent story, it's normal that people would want something a bit more fleshed out and consistent, but it's not.
It's just a small sneak peak at Toujou's life when she meets a guy who looks quite like Manaka. But isn't.
Honestly, I think this manga is enjoyable for what it is, and it was always nice to see some of the characters again after so long. Just don't go into this expecting a full fledged sequel, think of it more like a special side story and nothing more.