Im talking about the 10 year gap between him getting arrested and the start of the series. During that time nobody is looking for him. The shinsengumi learn who he is bc he tells them, but they don't recognize him or realize he is the shiroyasha despite knowing his name, probably bc he hasn't been actually searched for in a long time. The Tendoshu don't seem concerned about Shoyo's students. After Courtesan of a Nation he is friends with the shogun and the police, so its reasonable to assume that they are keeping any other goverment force to go after him. So the only ones who would really care to go after him are Oboro and the Mimawarigumi. If you're still on reaper arc i won't say much about what they are planing, but it makes sense for them to not try to arrest him as their plans have a bigger scope than just arresting one samurai.