From the studio's homepage Bulletin Board in 2009

制作遠藤達也 said:
合同ラリーのところは入江さん自ら作画をしております！

Struggled with believing this for a while because Kenji Irie wasn't also credited for KA. Normally, ADs were at least given bottom KA credit. For whatever reason, in these OVAs specifically they weren't listed.