If you liked the Air anime, the Anime-Planet community thinks you'd like:
Hamura Shou is a young man who has been searching for his long lost younger brother named Kai since childhood. After transferring to an all-boys school, he manages to find him – but Kai denies it, and him in the process. Meanwhile, in the magical world of Winfield, the white-winged beings of the royal family have been killed and exiled, leaving the throne to its enemies. Through a series of events, the link between Earth and Winfield will be revealed – a link which will turn friends against each other, and cause tragedies to occur.
Angel's Feather deals with a relationship between two brothers; Air deals with a wider range of relationships that the main characters have to deal with. However, both series are psychological in nature.
Karada is an elementary school student who acts mature for her age, and asks that people treat her like an adult. While praying at a wishing stone (negai ishi), she meets an older girl named Shouko. Shouko had moved to this small town to start a new life, but the same day she meets Karada, she encounters her brother, Hiro. Tension builds as Shouko and Hiro reflect on their past relationship while sending Karada home alone, and by the end of the day, both Shouko and Karada end up at the wishing stone hoping for change. Karada wishes to become an adult, while Shouko wishes for things to go back as they were in the past. That night under the bright moon, the wishing stone grants their wish, and an unbelievable transformation occurs: Shouko becomes a child and Karada becomes an adult. Now the two girls must struggle with their new bodies while finding a way to return back to what they once were.
Koyomi Araragi is an aloof boy who holds a strange, supernatural secret which inadvertently leads him to others with similar stories. Gods, spirits and afflictions can be pesky things, taking important memories or causing unusual tendencies – a fact that Koyomi and others are unfortunately aware of. Using the help of an eccentric homeless man, Koyomi is able to help new friends he meets along the way with their own paranormal conundrums…
At the core and it's visual style, these shows are quite differnt, but they are both set up as harem shows and it's only hinted that most of the girls are interested in the male lead in a romantic way. They both deal a bit with magical and supernatural powers, even if Bakemonogatari plays on that part much heavier than Air.
On an island where cherry blossoms bloom all year-round, love seems to always be in the air. It is in this magical atmosphere that Asakura Junnichi lives, and when he dreams he travels to the dreams of others, rather than have any of his own. In everyday high-school life, he is accompanied by his adopted sister, Nemu, and an eclectic group of friends including a j-pop idol-in-the-making and a girl they knew from their childhood. Promises, and magic, and love -- Junnichi seems to dream about every girl he knows, but which girl dreams of him...?
Both Air and Da Capo are harem in genre. They also both deal with issues one would have to face in a high school setting. In each series the main hero is trying to find out what is going on around him and how everything impacts the main heroine, the one that he loves. He also helps the other girls that like him.
Makoto Niwa has just moved from his rural hometown to live with his aunt and experience high school life in the big city first hand. Unfortunately, his dreams of an adolescence filled of dates and school activities are soon shattered by having to share his new home with Erio, his deluded cousin who thinks she's an alien and spends most of her time wrapped in a futon for protection! Now, in addition to enduring his aunt’s energetic attention and flirting awkwardly with the girls in his class, Makoto finds himself drawn into helping Erio rejoin regular society and stopping her 'alien' antics.
Both AIR and Denpa to Seishun Otoko boast a female cast of oddities and have an eccentric, main female character as the appeal. They have a bit of a random storyline that ends up making sense as the story progresses and they also have similar pacing.