There are not many differences with the original game and its objective is the same: to collect the blood of humans through a mosquito. As you advance level, humans become more difficult, so you must hit them at key points to relax them.
Rena 2: Hawaii no Atsui Yoru (minigame)
Like its predecessor, Ka 2 contains a hidden mini game - this time accessed by keeping Start pressed on the second controller as the game boots up. The star of this "Hot Night in Hawaii" is Rena, or at least one assumes so from the title and instructions, as this is a straight first person shooter.
The Game only consists of one single room that's swarming with mosquitoes, and the goal is to take out as many of them as possible within the time limit. Getting higher "combos" increases the score, accounting for at least a tiny minimum of strategy. For some reason Rena can duck and jump, although that doesn't really do much for her.