Ergo, for some, comics and manga might be a gateway to more graphic depictions of violence and sex, and for others, they're just a fun way to read stories about super-heroes and villains, about adolescence, adulthood, and all the trials that come with the mere process of growing up.
It can be Harry Potter, it can be Percy Jackson, it can be the Kingdom, Plato, O'Connor, Balzac or Rabalais. It can be the Alchemist, Lolita, Madame Bovary, The Adventures of Hucklebury Finn, 1984, anything. Some see the beauty that can be mined, another sees evil being condoned, sin being celebrated. The question is, as with most things, how are these tools being used, not the tools themselves. What one teaches is a component, how and why are more critical.
People protested, common sense prevailed and the returned swings felt like a momentary triumph over the gathering gloom. Guess what? Skinned knees returned to the park too. The reality is some in this world try to eliminate the possibility of skinned knees (whether physical or mental) without recognizing such a move also eliminates the discovery of flying through the air, of touching the sky, of racing your brother and fantasizing about going all the way around.
Things can be fantastical and not within the confines of the teaching of the Church and yet reveal Truth. All of Creation sings of the Glory of God, and Saint Paul could see the longing of those who did not know Christ, for a relationship with the Divine.
Imagination is one of God's cleverer ways of evangelizing His people, because the acts of creating in the mind is an imitation of the Creator. What we will into being by our efforts as art, is static, in that it will only be what we will it to be, in terms of its nuts and bolts and physical reality. It didn't exist for the world before we rendered it, but it reveals something of how our minds are like that of the mind that imagined us into being.
There is not pure wheat in art or literature, the wheat and chaff grow up together. Sacred art of the Vatican exists because those who created it studied the sacred and secular art that came before them. If we can only examine that which echoes our sensibilities, we will eventually learn nothing for fear of having our own spiritual bubble pierced.
Looking at the Saints' sensibilities, we ought not feel afraid. The Catholic imagination and mind understands beauty, truth, kindness and love, service and humility, these are universal calls of the heart. As such, the saints who are known both as scholars and artists would tend to indicate, when we enter into the world of arts and letters, our understanding of what is good, true and beautiful, is expanded, not contracted, whether by contrast, or by discovery. There are parts of the Canterbury tales I don't love, and Shakespeare plays I don't enjoy, yet I can see the good of knowing both. I don't need blinders placed on my mind to understand some of it is great, and some of it, less so, nor is my soul threatened by the reality of imperfect or non Sacred art.
To those who wring their hands at the choices of books, who think somehow, if we pull at this and tweak at that and cut this out, we'll create a safe spot, where no one will be injured, this is a lie. I suspect many who get snared, are trying (albeit in a blind manner) to bind the world so that nothing will ever happen. They're like Marlin at the beginning of the movie, not letting Nemo experience life for fear life will hurt. The tragedy for each of them, for all of them will be 1) if they succeed, and 2) if they don't but spend their lives trying to.