You need to set your console to UTF8.
If you want the standard 80x25, then you have to remove any "vga=..." option from the boot command line. To be able to change it at runtime, use SVGATextMode.
By default, it uses the Video ROMs glyphs, but you can load different glyphs into the video buffer (not ROM! - so it lasts only until reboot) using "setfont". Note that different fonts have different maps, because a VGA font usually has only 256 glyphs - no way to store all UTF8 characters - and many are different, e.g. some have russian at the high-byte range, some have "European" ... and whatnot. Some are ASCII(CP437)-coded, some are ISO coded. setfont got flags, ask if you need.