This series can be summed up as endearing and absolutely charming.
While the plot differs some from the classic book ("Daddy Long Legs" by Jean Webster) on which it was based, "My Daddy Long Legs" is still a tender coming-of-age tale centered around the plucky orphan Judy Abbott, who is sent to a prestigious all-girls high school by a mysterious benefactor she dubs 'Daddy Long Legs'.
The story is set in early 20th century America--and I have to say I was impressed by how accurately this anime depicted the fashions, architecture, technology and experiences of this setting and time period. If you like historical fiction, this is a great show to pick. This series is full of fun and (in the second half) romance. Judy and her friends Sallie and Julia get into many scrapes during their three years of high school, but if you don't mind watching some awkward experiences natural to the growing-up process, you'll enjoy all the episodes, not just the romantic ones near the end.
All-in-all, this is a fantastic, accurate depiction of the educated female experience in 1910s-1920s America. I plan on watching it again and again.