WeWork’s co-founder and former chief executive Adam Neumann sued SoftBank Group, accusing the Japanese technology group of breaking a key provision of a deal that gave SoftBank control of the shared office space company.

The civil complaint, filed in Delaware’s Chancery Court, is the latest legal tussle over SoftBank’s multibillion-dollar rescue of We Co., the parent of WeWork, and caps the dramatic falling out of SoftBank founder Masayoshi Son and Neumann.