Ah, I see they deployed the Kobo revival collab already. If you look at how Holostars EN are performing, I think you might notice a certain trend where the debut is their most viewed stream and the collab is their second most viewed stream with 3 of them with Kobo. The only one who has done better than their debut in views is Axel with his collab song with EN and ID but it's still not at 1 million views yet.
Gavis Bettel: Debut (276k- over 4 weeks), [Collab stream] The Boys are Back in Town (125k- over 4 weeks), A Big Surprise (71k- over 4 weeks). [2 videos over 100k]
Banzoin Hakka: Debut (260k- over 4 weeks), [Monetization Karaoke] Let's fund the Capyranch Hakkitos (62k- over 3 weeks), Raven's Paradigm (song) (205k- over 4 weeks) [3 videos over 100k]
Josuiji Shinri: Debut (228k- over 4 weeks), [Zatsudan] I want to stream (45k- over 4 weeks), Daddy Daddy Do (cover) (141k- over 4 weeks) [2 videos over 100k]
Machina x Flayon: Debut (297k- over 4 weeks), [Valorant] Epic Collab w/ Kobo (64k- over 14 hours), Kiss of Death (cover) (57k- over 9 days) [1 video over 100k]
Regis Altare: Debut (542k- over 6 months), Kobo is short [Valorant] (290k- over 5 months), Heartache (cover) (314k- over 6 months) [
Axel Sirios: Debut (357k- over 6 months), [Valorant] Baby sitting Altare's lil sis while the man is on his break (135k- over 3 months), Bad End Night (song) (792k- over 3 months) [9 videos over 100k]
Noir Vesper: Debut (329k- over 6 months), [Boomer vs Zoomer] No items, Fox only, Final Destination (212k- over 5 months), That stream that almost got me canceled (163k- over 3 months) [9 videos over 100k]
Magni Desmond: Debut (484k- over 6 months), [First Collab] Tempus Assembles (227k- over 6 months), Escape from the City (cover) (273k- over 3 months) [18 videos over 100k]
Without looking a JP stars, I think Holostars EN is doing better on the streaming front but are not there yet to surpass them on the music front because I think some Holostar JP already have MVs that surpass 1 million views already.