Shōnen and Seinen Anime and Manga

[odonata]

What are the manga and anime that could be shared by Shōnen and Seinen.
Where would you say the boundry is and how far could the boundry be pushed?

When can seinen and shōnen enjoy the same things?

[MMM]

I think Kazuo Umezu horror like the Scary Book series could fit in both.

[ILOVEJAPAN]

I was actualy just thinking of starting a thread about this. To me it feels like there isn't that much diffrence between shounen and seinen.

I think the main diffrence is in adult content. With Shoujo and Josei I think the main diffrence is level of maturity and sophistication, but with shounen and seinen it seems like if some shounen was just a bit edgier, and some seinen were just watered a little bit down, then they would meet in the middle.

Bassicly (and it depends on the sereise) I think there is a very thin line between some of the more adult shounen and some of the more imature seinen.