The Japan Aerospace Exploration Agency (JAXA) is currently studying the Hayabusa-follow-on missions to more primitive bodies. Hayabusa-2 is a replica to the Hayabusa spacecraft and will be ready for quick flight in less than four years. It will go to a C-type asteroid, while Hayabusa visited an S-type asteroid, Itokawa. And Hayabusa mk-II is much larger spacecraft that may go to an extinct comet, Wilson-Harrington. Both the spacecraft are propelled by the ion engines and the trajectory analysis results through an optimization process. The paper presents how those missions scenarios are built utilizing the ED VEGA strategy.