I love movies. I love going out to see a movie, I love to watch a good movie on cable or Netflix. Some of the movies I love are hard R rated. During the reboot I either did not watch them, or I actually closed my eyes or looked away during the sex scenes. Why? I knew they were going to trigger me.
Now, after I am rebooted, they do not trigger me. But that is because I took time away from them during the reboot. I cannot know your exact situation, but I do know that if there is the possibility a manga will trigger you, I advise giving it a break during the 90 day reboot. After that, it may be no big deal. During the reboot I would give the same advice for a lot of comic books, the ones that draw the impossibly built women wearing only dental floss; avoid it during the reboot. There is a method to getting clean and this is part of the method--taking time to re-sensitize the brain's reward pathways to realty. Your brain will rebalance, but you need to help it by not giving it any artificial dopamine spikes. Using anything that is not reality to get a dopamine spike is just prolonging the problem, not solving it.
I see a lot of guys here come up with reasons not to get clean,to keep using, to trigger, but, seriously, just get clean and you will have a completely new perspective on a lot of things, and a lot of things you have to avoid during the reboot will no longer be problematic for you. You will never be able to go back to watching porn of course, and you won't want to, but a lot of the things that trigger you during the reboot, the porn substitutes, etc., just won't trigger you after you successfully reboot. That takes about 90 days and I suggest you go hard mode unless you have a real, living and breathing sexual partner with a pulse that you can feel. And....I am not talking about your hand.
Peace.