Actual dialog in one issue: "he is so good at sports, its almost as though he was black".
Chapter 92 had a black character helping the other bullies extort money from people. List_of_Miscellaneous_Phase_1_Characters#Black_Member_of_Tachibana.27s_Gang
Izumi disguised himself as a black American before going on his killer rampage in the Shinjuku massacre.
On the mission at the dinosaur museum there were black American tourists dressed as gangster rappers.