The 'How Not to Summon a Demon Lord' sex comic is definitely not appropriate. It goes beyond what is considered acceptable in terms of decency and can have negative impacts on viewers' mindsets and values.
Avoiding this starts with having a good sense of what's appropriate and not getting into content that might be offensive or against the rights of the original creators. It's better to explore creative ideas that are positive and can be enjoyed by a wide range of people.