I highly recommend that manga, every Baki fan will love this spin off ! It gives us more depth into the lore and into the family of Kozue Matsumoto and also, we get to know Momo who is Katsumi's brother. Another cool thing is that finally Itagaki confirmed how the Garouden series shares a universe with Baki, so yeah, the cameos that happened in Baki are actually canon and not just an easter egg. The best characters are for sure Momo and Juumei Kuga, Juumei was my favorite by far as i already liked him from the Garouden manga and after seeing more of him,well, he just grew more with me.
After the series ended i am hyped to see where this will go considering Baki Raihen is being released now.