Here is probably the first painting of Miura that was ever published. It appeared in a special issue magazine that Hakusensha released between the last issue of Monthly ComiComi (December 1988 issue, released in October) and the first issue of Monthly Animal House (May 1989 issue, released in March), which took over from it.
It was called (コミック読本) ヒーロー大集合, which translates to "The great gathering of heroes", and likely came out in January 1989. It bridged the gap between the two and advertised Animal House's coming first issue. For more details about these magazines, please check this thread on SKnet.
Anyway, the magazine contains about 440 pages of forgettable (and forgotten) manga. What interests us is of course Miura's illustration, which is used here to showcase 王狼, pronounced おうろう (OUROU), translated in English as "King of Wolves".
This collaboration between Miura and writer Buronson was billed as the top series of Animal House's launch. It was also Miura's debut series as a professional mangaka, after having published two one-shots while in school (1985) and having had Berserk's prototype rewarded and published as part of Monthly ComiComi's 7th annual Manga School contest.
Berserk as we know it would begin its serialization later that year, in Animal House's October 1989 issue (released in late August). This painting serves to remind us of Miura's extraordinary talent and of the fact he found success pretty much immediately. He was 23 at the time.