The Kobe product may be similar to this Lincoln carbon steel flux/wire.
http://www.mylincolnelectric.com/LEExtranet/certs/pdf_lib/US58820_20050215.pdfSAW fluxes/wires that are designed to get acicular ferrite with low impurity levels, such as P, S, O, N, and probably some other trade secrets thrown in can get that toughness without nickel additions. Lincon's flux was just develped though, so I'm not sure how recently these toughness levels withot Ni have been achievable.
As for the H2S service, you should review a document such as NACE MR0175/ISO 15156 for the oil production side, or they have another one for refineries, but I can't remember that document is right now. The general principal is- not more than 1% Ni in the weld deposit, plus qualificaiton of the WPS by hardness testing. Then NACE has it's own set of essential variables that affect hardness that apply to the hardness tested WPSs. Items such as carbon equivalent of the base metal, PWHT, heat input, etc.