It looks more like kylinga except my flowers look different. it is a sedge like nutsedge. Although it is easier to pull out, there are still nuts. Nutsedge killer works. The best is sedge hammer. It is expensive and it is a powder that has to be reconstituted and used within hours. It does not keep. Image also works and both can be selective weed killers in some grasses. The grasses may still turn yellow, but usually survive if they ae healthy. It has to be applied before the seeds come out and use a post emergent like preen to stop the seeds from sprouting. Roundup will kill the nutsedge it contacts but you still need a preemergent to control the lseeds and like nutsedge, it does not kill any free nuts in the soil.
Cut your grass higher, aerate top dress, feed and water the lawn to keep it as healthy as possible to crowd out the weeds. Some grasses are better at crowding than others. If zoysias are managed well, they grow very thick and can crowd out a lot of weeds as long as they are healthy.
Nutsedge is an arduous process to eliminate. You will have to repeat spraying and preventing any sedge from seeding. It will literally take years before you can declare yourself free.
Happy gardening in Hawaii. Gardens are where people grow.