well it is Hayate Gekko

released at 24th December 2019 on CN server as Secret Ninja

hint 1: male

hint 2 Konoha

hint 3: strong cough

hint 4: guide chunin exam

why it cant be Genma ? because he was released at 30th june 2020 on CN servers in 3vs3 and is no secret ninja and because of the last two hints.

why cant it be Chiriku ? because he is now in the Secret Ninja paket

why cant it be Yota ? same reason like Chiriku

why cant it be Hiashi or Kotetsu ? both where secret Ninjas this year and cant be it two times in different seasons.

3rd hint: Dark eyes. Is it really Hayate?

yes because of his deep eye rings that he has because of his strong cough since his childhold till his death. When he was reanimated with EDO Tensei he did have dark black eyes too.