Sankei News reports (as translated by Kotaku and C-Sword on Shoryuken).
High Score Girl includes characters from SNK's The King of Fighters and Samurai Shodown more than 100 times, SNK claims. Square Enix says SNK never asked it to stop publishing the manga. High Score Girl is making the jump to anime, and SNK realized the infringement when a production company asked to use SNK's copyrighted characters and sounds in the show, the report says.
Pages of the manga in the SRK forum show High Score Girl also depicts Capcom's Street Fighter and NetherRealm's Mortal Kombat arcade games.
[Images: Square Enix]