Orphans are common in the world of anime, but most of them don't go through their whole childhoods alone. Rather, they have parental figures who step in and do the job their parents couldn't finish. In other cases, a character might not be an orphan, but might be another adult that takes on a parental role.
Let's celebrate some of the best parental substitutes in anime - after all, they've taken on some serious responsibility. Some of these characters meet their surrogate children through training: a great example of this is Izumi Curtis from Fullmetal Alchemist, who teaches the Elric brothers how to do alchemy. Others, like Akari Kawamoto of March Comes In Like A Lion, are more focused on their charges' emotional development and physical needs than mentoring them in any specific way.
Which ones are your favorites?
Although Piccolo and Goku were originally enemies, Piccolo still decides to take Goku's young son Gohan under his wing after Goku sacrifices himself in order to defeat Raditz. Piccolo isn't trying to be Gohan's father - rather, he's trying to make sure Gohan will be strong enough to fight in the looming Saiyan invasion. But as time passes, the two do develop something like a father-son relationship, one that persists even after Goku comes back to life and can resume his fatherly duties.
Probably because constant warfare leads to a whole lot of orphaned children, Naruto is actually full of surrogate parents. While there are plenty to choose from, let's take a look at Iruka Umino, the first parental figure in Naruto Uzumaki's life, and the one who would ultimately act as his 'father' when he married Hinata Hyuuga.
When Iruka and Naruto first meet, Iruka is Naruto's teacher at Ninja Academy. At first, Iruka is reluctant to deal with Naruto, because his own parents lost their lives in the Kyuubi attacks, and that Kyuubi was now sealed inside Naruto's body. Ultimately, Iruka came to regard Naruto not as a trauma trigger but as a little boy who reminded him very much of himself at that age. Iruka takes a special interest in Naruto, offering mentorships and even defending him with his life.
Ostensibly, Izumi Curtis' job was to teach Alphonse and Edward Elric how to use alchemy - and she definitely did do that. But somewhere along the way, she started thinking of the Elric brothers as her surrogate sons. This situation benefitted both parties - Ed and Al lost their mother to illness and their father hasn't been around for years. Meanwhile, Izumi Curtis gave birth to a stillborn baby, so her desire to be a mother is indeed powerful. Her feelings of parental affection for the boys doesn't mean she goes any easier on them during training, however - she's scarier than some of the enemies the two will face later in the series.
Izuku Midoriya has a mother who loves him very much, but his father has been working overseas for most of his life, and the two don't appear to have much of a relationship. Izuku finds his father figure in Toshinori Yagi, also known as All Might. Though Izuku has worshipped the pro hero for most of his life, they actually build a real relationship when All Might decides to take Izuku on as the heir to his quirk, One For All. All Might goes far beyond the responsibilities he has as Izuku's teacher, working with him, one-on-one, to mentor him in his development as a hero, and advising him on his personal life, too.