This will be Tuñacao's third defense of the crown he won after eking out a unanimous decision win over Thai Kumarnthong Por Pluemkamol on November 19, 2005 also in Tokyo.
In his previous bout on November 11 last year, the 28-year-old Tuñacao prevailed over Japanese Masahito Igawa by unanimous verdict over 10 heats.
Tuñacao, who is managed by Japanese businessman Yasuo "Machang" Matsuoka, holds a 21-1-3 win-loss-draw record spiked with 14KOs.
Tuñacao's only setback was dealt by Thai Pongsaklek Wonjongkam via stunning first round stoppage during his second defense of his WBC flyweight belt on March 2, 2001 in Pitchit, Thailand.
Lunas is no easy opponent for Tuñacao having reigned as PABA flyweight champion three times before relinquishing his throne to move up to the bantamweight ranks.
A veteran of 27 fights, Lunas sports a decent record of 20 wins - 11 by knockout - on top of six defeats and one draw.
The 23-year-old Lunas scored a smashing first round stoppage of Indonesian Billy Wuwungan the last time he fought on September 13 last year.