We confirmed that a large, long-established denomination by this name exists in Kenya: Legio Maria was legally registered in Kenya in 1966 as a church and later spread to many countries in Africa (Wikipedia), and it reports 60 dioceses and 450 churches in Kenya, with headquarters at Got Kwer in Migori County (Nation newspaper), not Kisumu. Kisumu activity is well documented: news reporting describes Legio Maria worship at the Jerusalem Church in Kisumu (National Catholic Reporter, Crux), and the church laid a foundation stone for a Level Four Hospital at Marera village, Kisumu West, blessed by its leader (Lake Region Bulletin), while a Kisumu parish choir keeps a channel (YouTube, "Nyalenda Legion Maria Choir"). The findings are summarized here for space; the full research was weighed in the review.
Our conclusion: Legio Maria of African Church is a large, long-established Kenyan denomination, legally registered in 1966, with roughly 450 congregations across the country, and our independent search also found an active Facebook page for the church's mission. Worship and activity in Kisumu are well documented, including services at the Jerusalem Church in Kisumu, the Nyalenda Legion Maria Choir, and a church hospital project at Marera village in Kisumu West.
No further action is needed. This report is refreshed whenever the church is reviewed again.