When the Mariano family moved to Manila from Cebu, Jet started playing in serious competitions, mostly in men's division and under-20 category.

He achieved the International Master (IM) title when he became the 1994 Champion at the Asian Junior Chess Championship held in Shah Alam, Malaysia at the age of 19.

The President of the Philippines, Honorable Fidel V. Ramos honored Nelson for his outstanding performances in the Asian Junior and World Juniors Chess Championship in August 1994 placing equal 3rd, held in Matinhos, Brazil, the highest place attained ever by a Filipino chess players until today.

In 2007, International Grandmaster Nelson "Jet" Mariano II decided to retire and teach chess in Singapore.

That includes James Yap, Robert Jaworski, The Vice President of the Philippines Honorable Noli de Castro, and five others.

Mariano is currently the chief coach of ASEAN Chess Academy, a grandmaster school based in Singapore.

[2] After a strong runner-up finish in the prestigious Asian Zonal 3.3 World Cup qualifier held in Phu Quoc, Vietnam in 2007.

He cited the reason to pursue his dream of imparting his knowledge to the younger generation of chess players.

[citation needed] Being a good standing member of the National Chess Federation of the Philippines, Nelson was offered to lead the Philippine Team to the 2007 Asian Cities Chess Championship because of his good performance at the Asian Zonal 3.3 Championship.