How can I leave my company by breaking the agreement?

I am working with a MNC in automobile sector. In 2014, they sent me to Japan HQ for on job training with a career objective sheet specifically mentioning my career role after two year training in Japan. But when I reached Japan nothing was clear about the objective sheet and I was working with them on different project. In the middle I informed my management about the issue and asked them to provide clear road-map of my responsibility and project after I return to India but nothing was provided. I was so much frustrated that I underwent hypertension and anxiety treatment because management said I can not quit Japan in between and if I leave I have to pay cost. Now I am returning to India after two years and they are asking me to do a different job and support Japan from India in their activities though it is not my major responsibility. I spent two years in Japan and signed a 3 year employment bond just to do a supporting job. I raised this issue with management and requested them to allow me work in Japan only in same project but they rejected. Now I am frustrated and I want to leave this company but cost of breaking agreement is very very high. Please suggest me how to proceed.