ni-san is shorth for oni-san (older brother) the prefix -san is formal given usaly after names. for older brother or someone a litle older than you extra: onee-san is older sister
Napansin kaagad ni Miss Sanchez ang kakatwang kilos at alingasngas ng kaniyang mga kanayon laban kina Kabo Lontoc na ibinunga ng bintang ni Aling Ambrosia na benggansa lamang ang dahilan ng pagdakip...