TOKYO — “Umizaru 4: Brave Hearts,” the fourth entry in the “Umizaru” action franchise about the Japanese Coast Guard, has topped 1.2 million admissions and $19 million at the box office in only four days on release, putting it on track to top the domestic B.O. for the year.Opening on Friday, instead of the usual Saturday, helmer Hasumi Eiichiro’s “Umizaru 4″ earned $3.03 million on 190,821 auds and 450 screens. It added more than 300,000 auds daily to drive its four-day total to 1,223,437. Based on a popular comic by Shuho Sato, the four pics star Hideaki Ito as an elite Coast Guard diver who performs spectacular rescues with the aid of his best buddy, played by Ryuta Sato. The stories are based on the actual exploits of a 36-man Coast Guard diver team. In the latest, Ito’s character, Daisuke Senzaki, answers the call when a jumbo jet hits the water, an incident inspired by the 2009 “miracle on the Hudson,” when all the passengers successfully evacuated a downed US Airways flight after the pilot ditched the plane in New York’s Hudson River. The third pic, “Umizaru 3: The Last Message,” topped $100 million in 2010, a series record and the No. 1 domestic live-action hit of the year. The franchise also generated a hit Fuji TV drama in 2005.