Akuma no Ororon is by Mizuki Hakase and ran in the monthly magazine Wings.
This manga first appeared in the April 1998 issue of Wings, and finished in the January 2001 issue.
It is 4 volumes long.

Tankoubon Info:

Volume 1:
ISBN 4-403-61539-2
524Y
First published 1999-05-10

Volume 2:
ISBN 4-403-61565-1
505Y
First published 1999-10-25

Volume 3:
ISBN 4-403-61591-0
520Y
First published 2000-06-10

Volume 4:
ISBN
520Y
First Published 2001-03-?