Nanaka Kirisato is a serious 17-year-old girl whose main goal in life is to study hard and grow up quickly. She doesn't have any friends, except for Nenji, whom she has known since her childhood. Although she constantly lectures him about his immaturity and fighting, he is the only one that stays by her side. One day after an argument with Nenji, Nanaka falls down a flight of stairs causing her to lose eleven years of her memories. Now she believes that she is a 6-year-old girl! Nenji decides to protect Nanaka by keeping her condition a secret so she can continue attending school and lead a normal life. With Nanaka’s childish personality and her unstable medical condition, how long will Nenji and Nanaka be able to keep up this charade?
Yukino had it all. Brilliant, athletic, popular and pretty, she was the perfect school girl with many friends and admirers. But then one fateful day she met her match: a handsome young man named Arima. Now, not only is he beating her at her own game, she's becoming more and more dismayed to learn that she's developing her first real feelings of romance. Can Yukino maintain her model student appearance, or will love ruin all her plans?
Sawamura Seiji is the most notorious delinquent at his high school -- always getting into fights and causing problems, leaving him single and unlucky with the ladies. After another long day of rejection, Seiji discovers that the love of his life might have finally appeared, but in the unlikeliest of places... his right hand?! Now, in addition to dealing with daily fights and the gossip of his classmates, Seiji must handle a new problem of embarassing proportions: Kasugano Midori, a pretty young girl in place of his hand, who happens to have fallen in love with him!
Both series are comedies with a little drama thrown in. In Midori Days and Nanaka 6/17 the lead male character gets into fights constantly and he also tries to take care of the female lead in one way or another. Also, both of the females have an illness that they are trying to overcome to get back to normal. When both of the females are ill (Nanaka having the mental capacity of a six year old and Midori being transformed into a right hand) they have the complete opposite personality of what they had when they were normal. They turn into talkative, outgoing, and somewhat childish girls. The main difference between the two anime is that Midori Days is very ecchi, while Nanaka 6/17 is not. I'm sure that if you liked one, you should give the other a try.
Tragedy struck Kotaro Higuchi as a child in the form of his mother's death in a car accident. But fate has a funny way of doing things, and years after the fact an angel-in-training named Misha decides to pay him a visit. Joined by his fellow elementary school students, and later by the nicest demon you'll ever meet, Kotaro and Misha will embark on a journey of laughs and love.
What draws these two shows together are how in depth the realism goes and the lightheartedness. Pita-Ten deals with Kotarou, a boy whose mother passed away, so he gets all the housework pushed on him while his dad is constantly gone at work. In a way, the shows show how lonely both Nanaka and Kotarou are, but manage to brighten up the situation with happy, cheerful characters who may get their spirits knocked down but not forever. Nanaka's mom also passes away, making her become a cold, busy perfectionist that only wants to move on and become an adult by studying and doesn't open up and enjoy teenage life like she should.
Take notice that unlike Nanaka 6/17, Pita-Ten involves around a cast just about out of elementary school, so connecting the two may be a lttle hard. The way a kid as young as Kotarou views his life won't be the same Nanaka views hers, because she is more mature, despite the injury to the head she received to make her childish. Pita-Ten also has fantasy elements, which Nanaka doesn't. Both shows still have the everyday, school life subject as one the main focuses of the shows, but other places are accompanied otherwise. The reality can hit home, but doesn't overfill it's limits to where it won't ever have a glint a light to sooth the drama.
The eccentric Suzumiya Haruhi wants nothing more than to meet aliens, time travelers and espers… but she’ll have to settle for the everyday Kyon instead! Along with the mysterious Itsuki and the vacant Mikuru, the duo forms the SOS Brigade – a club whose mission is to discover the mysteries of the world. Armed with a razor sharp wit and a skill for manipulation, Haruhi will stop at nothing to have fun at all costs, even at the expense of Mikuru’s dignity!
Both shows involve two standoffish, cold girls that have their brighter sides witnessed in both anime. Both stories also involve around the people they encounter, and how it affects both female and male leads. However, Haruhi Suzumiya has a more connceted cast that involve the plot, rather than with Nanaka 6/17 where the central focus of the show is Nenji and Nanaka.