How can I marry my boyfriend when my visa is near expiration?

Your question is unfortunately unclear and so my response is based on a number of assumptions about your situation that may or may not be correct. First, however long it may take, you must wait until your divorce is final otherwise, your subsequent marriage to your boyfriend will not be valid for immigration or any other purpose(s) Next, if you are presently in Unite States and you entered with a valid visa, it does not matter if that visa is expired or will expire, because, once you marry your US citizen boyfriend,you become an immediate relative of a US citizen and the fact that your visa is expired will not matter. Despite this, you can still get your green card in the the US without the need to travel overseas for your green card interview. Note however, if your visa expires, rather than for you to go to Japan to marry your boyfriend, it is better for him to return to the US, marry you here and file the I-130 and your green card application. Done this way, processing of your green card should take place before the end of this year. Because, my suggestions may be based on an incorrect assessment of your situation.

The validity of your visa has no effect on your eligibility to get married. You should wait until your divorce in the Philippines is finalized before getting married to your American fiance. After your marriage, your husband can petition for you to come live in the US as his spouse. The petition is filed on form I-130.

If you are in the US, you can get married and then file for your adjustment of status on the basis of marriage even if the I-94 is expired. If you are outside the US, you can enter the US while the visa is still valid, wait for the divorce to be final and then get married. As long as you are married to a US citizen and enter the US lawfully, you can adjust status to permanent residence even after your authorized period of stay expires.